SOLUTION: why does sin(theta + pi/2)= + cos theta ?

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why does sin(theta + pi/2)= + cos theta )?
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Try this:
sin(theta+(pi/2)) = sin(theta)*cos(pi/2) - cos(theta)*sin(pi/2)
= sin(theta)*0 - cos(theta)(1)
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= -cos(theta)
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So sin(theta+(pi/2)) does NOT equal cos(theta)
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Cheers,
Stan H.