An angle in standard position measures pi/2 radians, and p(0, 1) is on the terminal side of the angle. what is the value of the cosine of this angle
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Angles could be expressed in degrees or in radians. The relationship between the two could be easily explained by illustrating a circle. A semi-circle has a total angle of 180°. This is equal to a π radians. So if the angle is π/2, in degrees, that would be 180/2 = 90°. 

Then, determining the cosine 90° in a calculator would yield an answer of zero.