Prove that :

4 (sin⁴ 30° + cos⁴ 60°) - 3 (cos² 45° - sin² 90°) = 2

If sin x = cos x and x is acute, state the value of x.

If tan θ = cot θ and 0° ≤ θ ≤ 90°, state the value of θ.

If sin x = cos y; write the relation between x and y, if both the angles x and y are acute.