Answer
$${\text{Let }}u = \tan x$$
Work Step by Step
$$\eqalign{
& \int {{{\tan }^{10}}x{{\sec }^2}xdx} \cr
& {\text{The method to solve tis integral is :}} \cr
& {\text{Set }}u = \tan x,\,\,\,then\,\,\,\,\,du = {\sec ^2}xdx \cr
& \cr
& {\text{Apply the substitution}} \cr
& \int {{{\tan }^{10}}x{{\sec }^2}xdx} = \int {{u^{10}}du} \cr
& {\text{Then, using the power rule for integration we can solve}} \cr
& {\text{easily}}{\text{.}} \cr} $$