Question

Simplify for 2pts. cos1º + cos2º +cos178º + cos179º

Answer 1

Hello,

$cos\ (a)+cos\ (b)=2*cos\ ( \frac{a+b}{2} )*cos\ ( \frac{a-b}{2} )$

cos(1)+cos(179)+cos(2)+cos(178)=2 cos(90)*cos(89)+2 cos(90)*cos(88)
=2(cos(89)+cos(88))=4(cos(88.5)*cos(0.5))