Hello, jonathanraxa!
I don't understand . . .
Given that: .
what are the steps in solving: .
We don't have to solve the equation!
They gave us the answer! .
Can you give us the original wording of the problem?
The original equation factors out to:
(t-1)(2t+1)(4t^2+2t-1)=0
Since we know t is sin(18), the first two factors will not equal zero, which leaves the final one.
Put that into the quadratic formula and one of the roots you get is (-1+sqrt(5))/4
(-1+sqrt(5))/4=sin(18)