Trigonometry in the Coordinate Plane part 2

Instructor Katherine Cliff

Warm up:

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Simplify if possible

\[\frac{x+6x^2}{4+3x}\]

What is the exact value of \(\sin\left(\frac{\pi}{6}\right)\)?

Examples

Find the reference angle for each angle in standard position.

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\(135^\circ\)

A. \(315^\circ\)

B. \(495^\circ\)

C. \(45^\circ\)

D. \(225^\circ\)

\(1020^\circ\)

A. \(30^\circ\)

B. \(300^\circ\)

C. \(120^\circ\)

D. \(60^\circ\)

Examples

Find the reference angle for each angle in standard position.

\[\frac{7\pi}{6}\]

A. \(\frac{19\pi}{6}\)

B. \(\frac{\pi}{6}\)

C. \(\frac{13\pi}{6}\)

D. \(\frac{5\pi}{6}\)

\[-\frac{8\pi}{3}\]

A. \(-\frac{2\pi}{3}\)

B. \(\frac{4\pi}{3}\)

C. \(\frac{\pi}{3}\)

D. \(\frac{\pi}{6}\)

Reference angle theorem













Where is each trig function positive?

Example 1:

The terminal side of an angle \(\theta\) in standard position passes through the point (-3, -5). Calculate the values of the six trigonometric functions for \(\theta\).

The terminal side of an angle \(\theta\) in standard position passes through the point (-3, -5). Calculate the values of the six trigonometric functions for \(\theta\).

Example 2:

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The terminal side of an angle \(\theta\) in standard position passes through the point (-2, 4). Calculate the values of the six trigonometric functions for \(\theta\).

Example 2:

The terminal side of an angle \(\theta\) in standard position passes through the point (-2, 4). Calculate the value of \(\sin(\theta)\).

A. \(\frac{2}{\sqrt{5}}\)

B. \(-\frac12\)

C. \(-2\)

D. \(-\frac{1}{\sqrt{5}}\)

Example 3:

If \(\sin(\theta) = -\frac17\) and the terminal side of angle \(\theta\) falls in QIV, find the cosine of angle \(\theta\).

Example 4:

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If \(\cos(\theta) = -\frac{12}{13}\) and the terminal side of \(\theta\) falls in QIII, find the tangent of angle \(\theta\).

Example 4:

If \(\cos(\theta) = -\frac{12}{13}\) and the terminal side of \(\theta\) falls in QIII, find the tangent of angle \(\theta\).

A. \(-\frac{5}{12}\)

B. \(\frac{5}{12}\)

C. \(\frac{5}{13}\)

D. \(-\frac{5}{13}\)

Computing exact sines and cosines for special angles in the coordinate plane

  1. Find coterminal angle

  2. Find quadrant

  3. Find reference

  4. Use 2 and 3 to find sine or cosine value

Example: Compute \(\cos(585^\circ)\) exactly.

Example: Compute \(\sin\left(-\frac{4\pi}{3}\right)\) exactly.