### Home > INT3 > Chapter 9 > Lesson 9.1.7 > Problem 9-89

9-89.

**9-89.**Evaluate each of the following trig expressions without using a calculator. Homework Help ✎sin(180º)

sin(360º)

sin(–90º)

sin(510º)

cos(90º)

tan(–90º)

Every point on the unit circle is defined as (cos (*θ*), sin (*θ*)).

Where is 180° on the unit circle?

Where is the *y*-value at that point?

0

See part (a).

When an angle is negative, it opens clockwise from 0° on the unit circle.

Find an equivalent angle between 0° and 360° by subtracting 510 − 360. Notice that the reference

triangle is a 30°-60°-90° triangle. Find the sin (30°).

0.5

What is the *x*-value in this location?

0

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