Question 1158756
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As the "co" in "cosine" implies, it means we are talking about the cofunction to sine.


Through the use of this cofunction identity
{{{cos(x) = sin(pi/2 - x)}}}


we can say the following:
{{{cos(x) = sin(pi/2 - x)}}}


{{{cos(3pi/8) = sin(pi/2 - 3pi/8)}}}


{{{cos(3pi/8) = sin(4pi/8 - 3pi/8)}}}


{{{cos(3pi/8) = highlight(sin(pi/8))}}}


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Similarly,
{{{tan(x) = cot(pi/2 - x)}}}


{{{tan(2) = cot(pi/2 - 2)}}}


{{{tan(2) = cot(pi/2 - 4/2)}}}


{{{tan(2) = highlight(cot((pi-4)/2))}}}
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