(Cos (a+b)+cos (a-b))/sin (a+b)+sin (a-b)=ctga

Question

(Cos (a+b)+cos (a-b))/sin (a+b)+sin (a-b)=ctga

Comments

Плиииз ))

Answer 1

(cosacosb-sinasinb+cosacosb+sinasinb)/((sinacosb+cosasinb+sinacosb-cosasinb)=
=2cosacosb/2sinacosb=ctga