How do you use an addition or subtraction formula to write the expression as a trigonometric function of one number and then find the exact value given #cos(80)cos(10)-sin(80)sin(10)#?
1 Answer
Jun 1, 2018
Explanation:
#"using the "color(blue)"addition formula for cosine"#
#•color(white)(x)cos(x+-y)=cosxcosy∓sinxsiny#
#"the expression given is the expansion of"#
#cos(80+10)=cos90=0#
