Name ________________________________________ Date __________________ Class __________________
LESSON
17-2
Defining and Evaluating the Basic Trigonometric Functions
Reteach
To evaluate trigonometric functions for reference angles, you can use a
special right triangle made with the x-axis in the appropriate quadrant.
Here are the side lengths of special right triangles in the unit circle and
the signs of the trigonometric functions in each quadrant.
Example
Evaluate the trigonometric function without using a calculator: sin(−225°).
Step 1
Step 2
Step 3
Identify the coterminal
angle between 0 and 360°.
Use a special right triangle in the
appropriate quadrant.
Choose the correct side
length for sine or cosine
and use the correct sign.
−225° + 360° = 135°
sin( −225°) =
2
2
Evaluate the trigonometric functions without using a calculator.
2. cos( −120°)
1. sin 420°
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3. sin( −60°)
4. cos 495°
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