In Exercises valuefirst - valuelast, find the exact value of the cosine and sine of the given angle.

\(\theta = 0\)

\(\cos (0) = 1\)

\(\sin (0) = 0\)

\(\theta = \frac {\pi }{4}\)

\(\cos \left (\frac {\pi }{4} \right ) = \answer {\frac {\sqrt {2}}{2}}\)

\(\sin \left (\frac {\pi }{4} \right ) = \answer {\frac {\sqrt {2}}{2}}\)

\(\theta = \frac {\pi }{3}\)

\(\cos \left (\frac {\pi }{3}\right ) = \frac {1}{2}\)

\(\sin \left (\frac {\pi }{3}\right ) = \frac {\sqrt {3}}{2}\)

\(\theta = \frac {\pi }{2}\)

\(\cos \left (\frac {\pi }{2}\right ) = \answer {0}\)

\(\sin \left (\frac {\pi }{2}\right ) = \answer {1}\)

\(\theta = \frac {2\pi }{3}\)

\(\cos \left (\frac {2\pi }{3}\right ) = -\frac {1}{2}\)

\(\sin \left (\frac {2\pi }{3}\right ) = \frac {\sqrt {3}}{2}\)

\(\theta = \frac {3\pi }{4}\)

\(\cos \left (\frac {3\pi }{4} \right ) = \answer {-\frac {\sqrt {2}}{2}}\)

\(\sin \left (\frac {3\pi }{4} \right ) = \answer {\frac {\sqrt {2}}{2}}\)

\(\theta = \pi \)

\(\cos (\pi ) = -1\)

\(\sin (\pi ) = 0\)

\(\theta = \frac {7\pi }{6}\)

\(\cos \left (\frac {7\pi }{6}\right ) = \answer {-\frac {\sqrt {3}}{2}}\)

\(\sin \left (\frac {7\pi }{6}\right ) = \answer {-\frac {1}{2}}\)

\(\theta = \frac {5\pi }{4}\)

\(\cos \left (\frac {5\pi }{4} \right ) = -\frac {\sqrt {2}}{2}\)

\(\sin \left (\frac {5\pi }{4} \right ) = -\frac {\sqrt {2}}{2}\)

\(\theta = \frac {4\pi }{3}\)

\(\cos \left (\frac {4\pi }{3}\right ) = \answer {-\frac {1}{2}}\)

\(\sin \left (\frac {4\pi }{3}\right ) = \answer {-\frac {\sqrt {3}}{2}}\)

\(\theta = \frac {3\pi }{2}\)

\(\cos \left (\frac {3\pi }{2}\right ) = 0\)

\(\sin \left (\frac {3\pi }{2}\right ) = -1\)

\(\theta = \frac {5\pi }{3}\)

\(\cos \left (\frac {5\pi }{3}\right ) = \answer {\frac {1}{2}}\)

\(\sin \left (\frac {5\pi }{3}\right ) = \answer {-\frac {\sqrt {3}}{2}}\)

\(\theta = \frac {7\pi }{4}\)

\(\cos \left (\frac {7\pi }{4} \right ) = \frac {\sqrt {2}}{2}\)

\(\sin \left (\frac {7\pi }{4} \right ) = -\frac {\sqrt {2}}{2}\)

\(\theta = \frac {23\pi }{6}\)

\(\cos \left (\frac {23\pi }{6}\right ) = \answer {\frac {\sqrt {3}}{2}}\)

\(\sin \left (\frac {23\pi }{6}\right ) = \answer {-\frac {1}{2}}\)

\(\theta = -\frac {13\pi }{2}\)

\(\cos \left (-\frac {13\pi }{2}\right ) = 0\)

\(\sin \left (-\frac {13\pi }{2}\right ) = -1\)

\(\theta = -\frac {43\pi }{6}\)

\(\cos \left (-\frac {43\pi }{6}\right ) = \answer {-\frac {\sqrt {3}}{2}}\)

\(\sin \left (-\frac {43\pi }{6}\right ) = \answer {\frac {1}{2}}\)

\(\theta = -\frac {3\pi }{4}\)

\(\cos \left (-\frac {3\pi }{4} \right ) = -\frac {\sqrt {2}}{2}\)

\(\sin \left (-\frac {3\pi }{4} \right ) = -\frac {\sqrt {2}}{2}\)

\(\theta = -\frac {\pi }{6}\)

\(\cos \left (-\frac {\pi }{6}\right ) = \answer {\frac {\sqrt {3}}{2}}\)

\(\sin \left (-\frac {\pi }{6}\right ) = \answer {-\frac {1}{2}}\)

\(\theta = \frac {10\pi }{3}\)

\(\cos \left (\frac {10\pi }{3}\right ) = -\frac {1}{2}\)

\(\sin \left (\frac {10\pi }{3}\right ) = -\frac {\sqrt {3}}{2}\)

\(\theta = 117\pi \)

\(\cos (117\pi ) = \answer {-1}\)

\(\sin (117\pi ) = \answer {0}\)

In Exercises solveforanglefirst - solveforanglelast, find all of the angles which satisfy the given equation.

For the problems where you are prompted to type in an answer, type a response in the range \(0 \leq \theta < 2\pi \).

\(\sin (\theta ) = \frac {1}{2}\)

\(\theta = \frac {\pi }{6} + 2\pi k\) or \(\theta = \frac {5\pi }{6} + 2\pi k\) for any integer \(k\).
\(\cos (\theta ) = -\frac {\sqrt {3}}{2}\)

\(\theta = \answer {\frac {5\pi }{6}} + 2\pi k\) (Quadrant II) or \(\theta = \answer {\frac {7\pi }{6}} + 2\pi k\) (Quadrant III) for any integer \(k\).

\(\sin (\theta ) = 0\)

\(\theta = \pi k\) for any integer \(k\).

\(\cos (\theta ) = \frac {\sqrt {2}}{2}\)

\(\theta = \frac {\pi }{4} + 2\pi k\) or \(\theta = \frac {7\pi }{4} + 2\pi k\) for any integer \(k\).

\(\sin (\theta ) = \frac {\sqrt {3}}{2}\)

\(\theta = \answer {\frac {\pi }{3}} + 2\pi k\) (Quadrant I) or \(\theta = \answer {\frac {2\pi }{3}} + 2\pi k\) (Quadrant II) for any integer \(k\).

\(\cos (\theta ) = -1\)

\(\theta = (2k + 1)\pi \) for any integer \(k\).
\(\sin (\theta ) = -1\)

\(\theta = \frac {3\pi }{2} + 2\pi k\) for any integer \(k\).
\(\cos (\theta ) = \frac {\sqrt {3}}{2}\)

\(\theta = \answer {\frac {\pi }{6}} + 2\pi k\) (Quadrant I) or \(\theta = \answer {\frac {11\pi }{6}} + 2\pi k\) (Quadrant IV) for any integer \(k\).

\(\cos (\theta ) = -1.001\)

Since \(-1 \leq \cos (\theta ) \leq 1\), \(\cos (\theta ) = -1.001\) has no (real) solution.

In Exercises solvefortfirst - solvefortlast, solve the equation for \(t\). (See the remarks on page cosinesineequationsrealnumbers.)

\(\cos (t) = 0\)

\(t = \frac {\pi }{2} + \pi k\) for any integer \(k\).
\(\sin (t) = -\frac {\sqrt {2}}{2}\)

\(t = \frac {5\pi }{4} + 2\pi k\) or \(t = \frac {7\pi }{4} + 2\pi k\) for any integer \(k\).
\(\cos (t) = 3\)

Since \(-1 \leq \cos (t) \leq 1\), \(\cos (t) = 3\) has no (real) solution.

\(\sin (t) = -\frac {1}{2}\)

\(t = \frac {7\pi }{6} + 2\pi k\) or \(t = \frac {11\pi }{6} + 2\pi k\) for any integer \(k\).
\(\cos (t) = \frac {1}{2}\)

\(t = \frac {\pi }{3} + 2\pi k\) or \(t = \frac {5\pi }{3} + 2\pi k\) for any integer \(k\).
\(\sin (t) = -2\)

Since \(-1 \leq \sin (t) \leq 1\), \(\sin (t) = -2\) has no (real) solution.
\(\cos (t) = 1\)

\(t = 2\pi k\) for any integer \(k\).

\(\sin (t) = 1\)

\(t = \frac {\pi }{2} + 2\pi k\) for any integer \(k\).
\(\cos (t) = -\frac {\sqrt {2}}{2}\)

\(t = \frac {3\pi }{4} + 2\pi k\) or \(t = \frac {5\pi }{4} + 2\pi k\) for any integer \(k\).

In Exercises pointsfirst - pointslast, let \(\theta \) be the angle in standard position whose terminal side contains the given point then compute \(\cos (\theta )\) and \(\sin (\theta )\).

\(P(-7, 24)\)

\(\cos (\theta ) = -\frac {7}{25}\)

\(\sin (\theta ) = \frac {24}{25}\)

\(Q(3, 4)\)

\(\cos (\theta ) = \answer {\frac {3}{5}}\)

\(\sin (\theta ) = \answer {\frac {4}{5}}\)

\(R(5, -9)\)

\(\cos (\theta ) = \frac {5\sqrt {106}}{106}\)

\(\sin (\theta ) = -\frac {9\sqrt {106}}{106}\)

\(T(-2, -11)\)

\(\cos (\theta ) = \answer {-\frac {2\sqrt {5}}{25}}\)

\(\sin (\theta ) = \answer {-\frac {11\sqrt {5}}{25}}\)

In Exercises findthevaluefirst - findthevaluelast, use the results developed throughout the section to find the requested value.

If \(\sin (\theta ) = -\frac {7}{25}\) with \(\theta \) in Quadrant IV, what is \(\cos (\theta )\)?

\(\cos (\theta ) = \frac {24}{25}\).
If \(\cos (\theta ) = \frac {4}{9}\) with \(\theta \) in Quadrant I, what is \(\sin (\theta )\)?

\(\sin (\theta ) = \answer {\frac {\sqrt {65}}{9}}\).

If \(\sin (\theta ) = \frac {5}{13}\) with \(\theta \) in Quadrant II, what is \(\cos (\theta )\)?

\(\cos (\theta ) = -\frac {12}{13}\).
If \(\cos (\theta ) = -\frac {2}{11}\) with \(\theta \) in Quadrant III, what is \(\sin (\theta )\)?

\(\sin (\theta ) = \answer {-\frac {\sqrt {117}}{11}}\).

If \(\sin (\theta ) = -\frac {2}{3}\) with \(\theta \) in Quadrant III, what is \(\cos (\theta )\)?

\(\cos (\theta ) = -\frac {\sqrt {5}}{3}\).
If \(\cos (\theta ) = \frac {28}{53}\) with \(\theta \) in Quadrant IV, what is \(\sin (\theta )\)?

\(\sin (\theta ) = \answer {-\frac {45}{53}}\).

If \(\sin (\theta ) = \frac {2\sqrt {5}}{5}\) and \(\frac {\pi }{2} < \theta < \pi \), what is \(\cos (\theta )\)?

\(\cos (\theta ) = -\frac {\sqrt {5}}{5}\).
If \(\cos (\theta ) = \frac {\sqrt {10}}{10}\) and \(2\pi < \theta < \frac {5\pi }{2}\), what is \(\sin (\theta )\)?

\(\sin (\theta ) = \answer {\frac {3 \sqrt {10}}{10}}\).

If \(\sin (\theta ) = -0.42\) and \(\pi < \theta < \frac {3\pi }{2}\), what is \(\cos (\theta )\)? (Round your answer to four decimal places.)

\(\cos (\theta ) = -\sqrt {0.8236} \approx -0.9075\).
If \(\cos (\theta ) = -0.98\) and \(\frac {\pi }{2} < \theta < \pi \), what is \(\sin (\theta )\)?

\(\sin (\theta ) = \sqrt {0.0396} \approx \answer {0.1990}\).

In Exercises calculatorfirst - calculatorlast, use your calculator to approximate the given value to three decimal places. Make sure your calculator is in the proper angle measurement mode!

\(\sin (78.95^{\circ })\)

\(\sin (78.95^{\circ }) \approx 0.981\)
\(\cos (-2.01)\)

\(\cos (-2.01) \approx \answer {-0.425}\)

\(\sin (392.994)\)

\(\sin (392.994) \approx -0.291\)
\(\cos (207^{\circ })\)

\(\cos (207^{\circ }) \approx \answer {-0.891}\)

\(\sin \left ( \pi ^{\circ } \right )\)

\(\sin \left ( \pi ^{\circ } \right ) \approx 0.055\)
\(\cos (e)\)

\(\cos (e) \approx \answer {-0.912}\)

In Exercises decomposebasicsinecosinefirst - decomposebasicsinecosinelast, write the given function as a nontrivial decomposition of functions as directed.

For \(f(t) = 3t + \sin (2t)\), find functions \(g\) and \(h\) so that \(f=g+h\).

One solution is \(g(t) = 3t\) and \(h(t) = \sin (2t)\).
For \(f(\theta ) = 3\cos (\theta ) - \sin (4\theta )\), find functions \(g\) and \(h\) so that \(f=g-h\).

One solution is \(g(\theta ) = 3 \cos (\theta )\) and \(h(\theta ) = \sin (4 \theta )\).
For \(f(t) = e^{-0.1t} \sin (3t)\), find functions \(g\) and \(h\) so that \(f=gh\).

One solution is \(g(t) = e^{-0.1t}\) and \(h(t) = \sin (3t)\).
For \(r(t) = \frac {\sin (t)}{t}\), find functions \(f\) and \(g\) so \(r = \frac {f}{g}\).

One solution is \(f(t) = \sin (t)\) and \(g(t) = t\).
For \(r(\theta ) =\sqrt {3 \cos (\theta )}\), find functions \(f\) and \(g\) so \(r = g \circ f\).

One solution is \(f(\theta ) = 3 \cos (\theta )\) and \(g(\theta ) = \sqrt {\theta }\).

For each function \(S(t)\) listed below, compute the average rate of change over the indicated interval. What trends do you notice? Be sure your calculator is in radian mode!

\[ \begin{array}{|r||c|c|c|} \hline S(t) & [-0.1, 0.1] & [-0.01, 0.01] &[-0.001, 0.001] \\ \hline \sin (t) &&& \\ \hline \sin (2t) &&& \\ \hline \sin (3t) &&& \\ \hline \sin (4t) &&& \\ \hline \end{array} \]

As we zoom in towards \(0\), the average rate of change of \(\sin (k t)\) approaches \(k\).

\[ \begin{array}{|r||c|c|c|} \hline S(t) & [-0.1, 0.1] & [-0.01, 0.01] &[-0.001, 0.001] \\ \hline \sin (t) & \approx 0.9983 & \approx 1 & \approx 1 \\ \hline \sin (2t) & \approx 1.9867 & \approx 1.9999 & \approx 2 \\ \hline \sin (3t) & \approx 2.9552 & \approx 2.9995 & \approx 3 \\ \hline \sin (4t) & \approx 3.8942 & \approx 3.9989 & \approx 4 \\ \hline \end{array} \]
In Exercises motionfirst - motionlast, find the equations of motion for the given scenario. Assume that the center of the motion is the origin, the motion is counter-clockwise and that \(t = 0\) corresponds to a position along the positive \(x\)-axis. (See Equation equationsforcircularmotion and Example EarthRotationEx.)
A point on the edge of the spinning yo-yo in Exercise spinningyoyo from Section RadianMeasure.

Recall: The diameter of the yo-yo is 2.25 inches and it spins at 4500 revolutions per minute.

\(r = 1.125\) inches, \(\omega = 9000 \pi \, \frac {\text {radians}}{\text {minute}}\), \(x = 1.125 \cos (9000 \pi \, t)\), \(y = 1.125 \sin (9000 \pi \, t)\). Here \(x\) and \(y\) are measured in inches and \(t\) is measured in minutes.

The yo-yo in exercise yoyotrick from Section RadianMeasure.

Recall: The radius of the circle is 28 inches and it completes one revolution in 3 seconds.

\(r = 28\) inches, \(\omega = \frac {2\pi }{3} \, \frac {\text {radians}}{\text {second}}\), \(x = 28 \cos \left (\frac {2\pi }{3} \, t \right )\), \(y = 28 \sin \left (\frac {2\pi }{3} \, t \right )\). Here \(x\) and \(y\) are measured in inches and \(t\) is measured in seconds.
A point on the edge of the hard drive in Exercise harddrive from Section RadianMeasure.

Recall: The diameter of the hard disk is 2.5 inches and it spins at 7200 revolutions per minute.

\(r = 1.25\) inches, \(\omega = 14400 \pi \, \frac {\text {radians}}{\text {minute}}\), \(x = 1.25 \cos (14400 \pi \, t)\), \(y = 1.25 \sin (14400 \pi \, t)\). Here \(x\) and \(y\) are measured in inches and \(t\) is measured in minutes.

A passenger on the Big Wheel in Exercise giantwheelmotion from Section RadianMeasure.

Recall: The diameter is 128 feet and completes 2 revolutions in 2 minutes, 7 seconds.

\(r = 64\) feet, \(\omega = \frac {4\pi }{127} \, \frac {\text {radians}}{\text {second}}\), \(x = 64 \cos \left (\frac {4\pi }{127} \, t \right )\), \(y = 64 \sin \left (\frac {4\pi }{127} \, t \right )\). Here \(x\) and \(y\) are measured in feet and \(t\) is measured in seconds
Consider the numbers: \(0\), \(1\), \(2\), \(3\), \(4\). Take the square root of each of these numbers, then divide each by \(2\). The resulting numbers should look hauntingly familiar.
On page ??, we see that the sine and cosine functions of angles can be considered functions of real numbers. With help from your classmates, discuss the domains and ranges of \(f(t) = \sin (t)\) and \(g(t) = \cos (t)\). Write your answers using interval notation.
Another way to establish Theorem cosinesinecircle is to use transformations. Re-read the discussion following Theorem standardcirclealternate in Chapter TheConicSections and transform the Unit Circle, \(x^2+y^2 = 1\), to \(x^2 + y^2 = r^2\) using horizontal and vertical stretches. Show if the coordinates on the Unit Circle are \((\cos (\theta ), \sin (\theta ))\), then the corresponding coordinates on \(x^2+y^2 = r^2\) are \((r \cos (\theta ), r \sin (\theta ))\).
In the scenario of Equation equationsforcircularmotion, we assumed that at \(t=0\), the object was at the point \((r,0)\). If this is not the case, we can adjust the equations of motion by introducing a ‘time delay.’ If \(t_{0} > 0\) is the first time the object passes through the point \((r,0)\), show, with the help of your classmates, the equations of motion are \(x = r \cos (\omega (t - t_{0}))\) and \(y = r \sin (\omega (t-t_{0}))\).