Posted by **unknown** on Sunday, November 20, 2011 at 5:17pm.

tan theta= 15/8 and pi< theta<3pi/2

a. Sin(- theta)

b. cos2theta

c. sin( theta - 3pi/4)

d. cos(theta/2)

can someone explain to me how do you find the exact value for these?

- math -
**Steve**, Sunday, November 20, 2011 at 10:44pm
the angle is in the 3rd quadrant.

So, draw a diagram where the hypotenuse extends down to the left from (0,0)

Since tan = y/x, this means that y = -15 and x = -8. So the hypotenuse of your triangle goes from (0,0) to (-8,-15), length=17

Now you are ready to go.

sin theta = y/h = -15/17

cos theta = x/h = -8/17

Use these values in your double-angle, half-angle, and sum/difference formulas.

## Answer this Question

## Related Questions

- Trig - 1. Establish the identity: sin(theta+3pi/2)=-cos(theta) 2. Find the exact...
- Calculus - I wanted to confirm that I solved these problems correctly (we had to...
- Math - 1. Let (-7, 4) be a point on the terminal side of (theta). Find the exact...
- Trigonometry - Thank you STEVE!!!!! Suppose that Cos (theta) = 1/square root 2 ...
- Precalculus(NEED HELP ASAP PLEASE!!) - cot(theta)= 3 pi < theta < 3pi/2 ...
- Precalculus check answers help! - 1.) Find an expression equivalent to sec theta...
- Precalculus check answers help! - 1.) Find an expression equivalent to sec theta...
- Algebra II - Multiple Choice Which expression is NOT equivalent to 1? (theta) ...
- trig - If sin theta is equal to 5/13 and theta is an angle in quadrant II find ...
- Math - angle theta is in the standard position and 0'=<theta=<180'. If cos...

More Related Questions