How to prove that sin (pi/2 - theta) = cos theta ?

1 Answer
Jim G.
Mar 13, 2016

see explanation

Explanation:

using appropriate color(blue)" Addition formula "

• sin(A ± B) = sinAcosB ± cosAsinB

hence sin(pi/2 -theta) = sin(pi/2) costheta - cos(pi/2)sintheta

now sin(pi/2) = 1 " and " cos(pi/2) = 0

hence sin(pi/2)costheta - cos(pi/2)sintheta = costheta - 0

rArr sin(pi/2 - theta ) = costheta

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