?

I have 2 equations

(r1+r2)^2=(r1+r3)^2+r4^2-2(r1+r3)r4cos(theta)

and

r1^2=(r1+r3)^2+r5^2-2r5(r1+r3)cos(theta-phi)

and I need theta and r1. I know phi,r2,r3,r4 and r5.