How do you evaluate $cos (pi/2) cos(pi/7) + sin(pi/2) sin(pi/7)$ ?

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Answer 1 · 2016-10-16T09:28:26

Inserting $cos(pi/2)=0 and sin(pi/2)=1$ in the given expression we get

$cos(pi/2)cos(pi/7)+sin(pi/2)sin(pi/7)$

$=0xxcos(pi/7)+1xxsin(pi/7)$

$=sin(pi/7)=0.434$

How do you evaluate cos (pi/2) cos(pi/7) + sin(pi/2) sin(pi/7) cos (pi/2) cos(pi/7) + sin(pi/2) sin(pi/7)?