Posted by **Shasha** on Tuesday, November 27, 2012 at 11:04pm.

What is the exact value of sin(2 theta) if cos (theta)=3/5 and (theta) is in quadrent 4?

12/25

24/25

-12/25

-7/25

-24/25

- calculus -
**Jennifer**, Wednesday, November 28, 2012 at 3:13pm
cos(theta) = 3/5

Use your calculator:

cos-1(3/5) = theta = 53.13 degrees

This is the value that your calculator gives, and it is in quadrant; To find the value theta corresponding to quadrant 4, notice the symmetry in a graph of cos x, which is that cos(x), cos(x) = cos(360 - x); 306.87 = theta in quadrant 4

quadrant 1 (0 - 90 degrees)

quadrant 2 (90 - 180 degrees)

quadrant 3 (180 - 270 degrees)

quadrant 4 (270 - 360 degrees)

Use your calculator to calculator sin(2*306.87)

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