How do you solve alpha and beta for these two equations?

i tried but it gives me a math error

the answers are

The hint is:

solve the 1st equation for cos(beta) first

then 2nd equation for sin(beta)

then square each equation (cos(beta))^2 + (sin(beta))^2 = 1

thats what i did but my answer at last part gives me

alpha gives a math error for this equation

thank you very much