# Pre Calculus

use the sum of difference formula what is sin(pi/2-5pi/3)?

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1. sin(a-b) = sin a cos b - cos a sin b

sin(pi/2-5pi/3) = 1 cos(5 pi/3) - 0

= cos (5 pi/3)

= cos (2pi - (pi/3))

= cos (-pi/3)

= cos 60 deg

= 1/2

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