=

Adding the powers : -4 + -2 = -6

Since all are even nos, we will divide each by cos⁶x to convert into positive power

So, =

=

= { since sec²x = 1 + tan²x}

= ( apply (a + b)² = a² + b² + 2ab )

Let tanx = t, so dt = d(tanx) = sec²xdx

So,

Put t and dx in the above equation,

=

=

=

=

=

=

= {1/tanx = cotx)