Question

Use angle addition formula to find the expression for cos(a+b). Use the same formula to

find cos(a+a).

Answer 1

What they said!!!!!!!!!!!!

Answer 2

we have

Cos (a+b)=Cos aCosb-SinaSinb

for

Cos (a+a)=Cos aCosa-SinaSina=Cos²a-Sin²a

is a required answer.