how do you prove if this is a true statement or not? Is this correct?

Question

 Is sin2xsinx-cosx = -(3root3)/2 true for 7pi/6? Explain.

 

Here is what I got:

sin(2(7pi/6)) = root3 / 2 (0.86602540378)

sin(7pi/6) = -1/2 (-.5)

cos(7pi/6) = -root3 /2 (-0.86602540378)

sin2xsinx-cosx = -(3root3)/2 ?

(root3/2)(-1/2) - (-root3/2) = -(3root3)/2 ?

root3 /4 (0.43301270189) = -(3root3)/2 ?

NO it is not correct

 

Answer 1

Your answer is the same one I got doing several methods. Are you sure that it is written correctly? Any parentheses missing?

 

Dorene O