I have tried using an expression for and got nowhere
I think maybe you're confusing π/15 radians with 15 degrees! Try tan(5θ) instead of tan(4θ). If you put the expression for tan(5θ) equal to √3, you'll get a fifth-degree equation one of whose roots is –√3. Divide out by the factor t+√3 and you'll be on the right track.
I think maybe you're confusing π/15 radians with 15 degrees! Try tan(5θ) instead of tan(4θ). If you put the expression for tan(5θ) equal to √3, you'll get a fifth-degree equation one of whose roots is –√3. Divide out by the factor t+√3 and you'll be on the right track.
I never thought of using at all! So the general solution is given by excluding the solution ( i.e. r = 3) as this corrospends to