Question 971520: Which of the following are solutions to the equation sinx cosx = -1/4 ? Check all that apply.
a. 7pi/6 + npi
b. 7pi/12 +npi
c. 7pi/12 +npi/2
d. 11pi/12 +npi
(Please help me, thank you)
Answer by Boreal(15235)   (Show Source):
You can put this solution on YOUR website! I don't like any of the choices.
At 45 degrees, or pi/4, sin x and cos x are equal and their product is 1/4. Each is sqrt (2)/2.
One must be negative.
Second and fourth quadrants are where this happens. Cosine is negative in the second, and sine negative in the fourth.
I would say 3pi/4 and 7 pi/4.
In the problem above, a and d give negative results but not the product. I tried the sum of the two, but that didn't work, either.
Was there anything else in the equation?
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