Long Jump Question - Net forces

[Chadlyacus]

Homework Statement

A Long-Jump Contestant experiences at the instant of landing, a gravitational force of 538N [Downwards], and a force applied by the ground to the feet, of 6382N [28.3 degrees above the horizontal]

(The answer is given in the book, being 6.15 X 10^3 N [23.9 Degrees above the Horizontal]
I just can't find out how to get there.
I have no idea on how to start this equation.

 

[LowlyPion]

Welcome to PF.

So what is the question?