Find , when:
If cos y = x cos (y + a), prove that .
Let us differentiate the whole equation w.r.t x
Formula :
According to chain rule of differentiation
According to product rule of differentiation
Therefore ,
( Multiply and divide by cos (y+a) )
(Since cos y = x cos (y + a))
(Formula sin(a-b)=sin a cos b – cos a sin b)