Question 647516: Refer to the graph of y = sin x or y = cos x to find the exact values of x in the interval [0, 4π] that satisfy the equation. (Enter your answers as a comma-separated list.)
3 cos x = 3/2
Answer by DrBeeee(684)   (Show Source):
You can put this solution on YOUR website! Given
(1) 3cos(x) = +3/2
Dividing through by 3 we get
(2) cos(x) = +1/2
Using Invcos(.5) we get
(3) x = + or - 60 degrees, or
(4) x = 60, 300
Adding 360 degrees to each yields the next pair of angles whose cosine is .5
(5) x = 60 + 360 and 300 + 360 or
(6) x = 420, 660
Those angles that satisfy x = [0,720] are
(7) x = {60, 300, 420, 660}
The next angle whose cosine is .5 is 420+360 or 780, which is outside the domain of answers.
Answer: x = {60,300,420,660}
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