verify the identity: sin(a+B) / cosa cosB = tana + tanB

Question

please help 

Answer 1

Hi Alma,

 

sin(a+B) / cosacosB ? tana + tanB

 

sin(a+B) = sinacosB + cosasinB (identity)

 

sin(a+B) / cosacosB = (sinacosB + cosasinB) / (cosacosB)

= sinacosB/cosacosB + cosasinB/cosacosB

= sina/cosa + sinB/cosB

= tana + tanB