For the power series of inverse tan (x) the geometric series is:

1 - t ^2 + t^ 4 - t^ 6 +...+ t^( 4n)

find the sum and hence prove that for 0 < t < x:

1/(1+t2) < 1 - t^2 + t^ 4 - t^ 6 +...+ t^(4n)

I havent got a clue how to approach this.

thanks

jacs