9514 1404 393
Answer:
(A) -1
Explanation:
I find it easiest to determine the angles x and y, then find the sine of their difference.
x = arccos(1/2) = 60°
y = arcsin(1/2) = 180° -30° = 150° . . . . . . for 2nd-quadrant angle
Then ...
sin(x -y) = sin(60° -150°) = sin(-90°)
sin(x -y) = -1
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Alternatively, you can find the other trig functions of the angles and use the formula for the sine of a difference.
sin(x) = √(1 -(1/2)²) = (√3)/2
cos(y) = -√(1 -(1/2)²) = -(√3)/2 . . . . 2nd quadrant angle
Then ...
sin(x -y) = sin(x)cos(y) -cos(x)sin(y)
sin(x -y) = (√3)/2·(-√3)/2 -(1/2)·(1/2) = -3/4 -1/4
sin(x -y) = -1