Question

Find the value of cos2theta if 2sin2theta = 90°

Answer 1

$given - \\ 2 \sin(2θ) = 90 \\ \sin(2θ) = 45 \\ by \: using \: identity \\ \\ {cos}^{2} θ - {sin}^{2} θ = \cos(2θ) \\ 1 - 2 {sin}^{2} θ = \cos(2θ) \\ 1 - 2 {(45)}^{2} = \cos(2θ) \\ - 4049 = \cos(2θ)$
◆I don't know why is this coming

But w.r.t to your question this answer us perfectly correct✔️✔️