P(1) is true
Let as assume P(k) is true

To prove P(k+1) is true using P(k).
P(k+1) =
            = …………….(1)
L.H.S of (1)

            =
            =
            =
            =
            =
            = =
P(K+1) is true.
By the Principle of mathematical induction, P(n) is true for all values of n where n N
Hence proved.