2·α + β = pi
(quadrilateri inscritti!!)
COS(α) = 1/4
SIN(α) = √(1 - (1/4)^2)---> SIN(α) = √15/4
SIN(2·α) = 2·SIN(α)·COS(α)
SIN(2·α) = 2·(√15/4)·(1/4)----> SIN(2·α) = √15/8
SIN(2·α) = SIN(pi - β)--->SIN(pi - β) = SIN(β)
√15/8 = SIN(β)
√(1 - (√15/8)^2) = COS(β)
7/8 = COS(β)
TAN(β) = √15/8/(7/8)----> TAN(β) = √15/7