Explain and use the complementary-angle relationship between sine and cosine.
Rewrite cosine of an acute angle as sine of its complement
Problem
Compute the complement of \(60°\) and use \(\cos(θ)=\sin(90°-θ)\) to rewrite \(\cos(60°)\) as a sine expression.
Big Picture
What this problem is really about
A cosine-to-sine cofunction rewrite changes both the function name and the angle. We’ll calculate the acute complement, apply cosine of an angle equals sine of its complement, and check the equivalence using the corresponding exact special-angle values.
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