If cos y = x cos (a + y), where prove that
Here,
cos y = x cos (a + y), where cos a
Differentiating both sides with respect to x, we get
Multiplying the numerator and the denominator by cos(a+y) on th RHS we have,
[Given cos y = x cos (a + y)]
[ sin(a-b)=sina cosb - cosa sinb]
Hence Proved.