Roots of equation

• Jan 15th 2012, 02:32 PM
razemsoft21
Roots of equation
Hi, can anyone help me to prove this:

If the roots of the equation

$x^3-Lx^2+mx+n=0$

are the cosine of the angles of a triangle

show that: $L^2=2m+2n+1$
• Jan 15th 2012, 07:01 PM
TKHunny
Re: Roots of equation
Well, you have three angles. Use them and see what happens.

$\alpha$, $\beta$, $\pi - \alpha-\beta$

You have a Law of Cosines.

Show us what you get.