Question 1189940


1. Express {{{cos(38) + cos(106)}}} as a PRODUCT.

use Sum-to-Product Identity:  {{{cos(alpha) + cos(beta) = 2cos((alpha +beta)/2) *cos((alpha - beta)/2)}}}


{{{cos(38) + cos(106)=2cos((38 +106)/2)* cos((38 - 106)/2)}}}

{{{cos(38) + cos(106)=2cos(72)* cos(-34)}}}



2. Express {{{cos(234 )cos(125) }}}as SUM


use Product-to-Sum Identity: {{{cos(alpha) cos(beta)  =(1/2) (cos(alpha - beta) + cos(alpha + beta)) }}}


{{{cos(234 )cos(125) =(1/2) (cos(234 - 125) + cos(234 + 125)) }}}

{{{cos(234)cos(125) =(1/2) (cos(109) + cos(359))}}}