We are given that,

4 cos^-1 x + sin^-1 x = π …(i)

We need to find the value of x.

Using the property of inverse trigonometry,

Replacing θ by x, we get

Substituting the value of sin^-1 x in (i),

4 cos^-1 x + sin^-1 x = π

Taking cosines on both sides,