Think of the unit circle. (circle with radius 1 and centered at (0,0)). There are 2pi radians total. It's often helpful to get rid of negatives by just adding 2pi repeatedly (going 2pi around the circle leaves you at the same spot, but it makes you less error prone). Doing that gives me sin(pi/2). That is a quarter circle from the right. You are at the top there. The y value = 1. So the sin(-3pi/2) = 1.
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Think of the unit circle. (circle with radius 1 and centered at (0,0)). There are 2pi radians total. It's often helpful to get rid of negatives by just adding 2pi repeatedly (going 2pi around the circle leaves you at the same spot, but it makes you less error prone). Doing that gives me sin(pi/2). That is a quarter circle from the right. You are at the top there. The y value = 1. So the sin(-3pi/2) = 1.
sin(-3Ï/2) = sin(Ï/2) = 1