Posted by Shasha on .
What is the exact value of sin(2 theta) if cos (theta)=3/5 and (theta) is in quadrent 4?
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calculus 
Jennifer,
cos(theta) = 3/5
Use your calculator:
cos1(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) 
calculus 
Chris,
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