Question

if cot (a+b)=0 then write the value of sin(a+2b)

Answer 1

if cot(a+b)=0 so cos(a+b)/sin(a+b)=0 so cosacosb=sinasinb sin(a+2b)=sinacos2b+cosasin2b=sina(1-2sin^2b)+2cosacosbsinb=sina-2sin^2bsina+2cosacosbsinb now we take common -2sinb(cosacosb-sinasinb)+sina using above result we get sin(a+2b)=sina