If tan (45° + θ) = 1 + sin 2θ, where $-\frac{\pi}{4}< θ <\frac{\pi}{4},$ then what is the value of cos 2θ?

Let sin 2θ = cos 3θ, where θ is acute angle. What is the value of 1 + 4 sin θ? (given that $\sin 18^\circ =\frac{\sqrt 5 - 1}{4}$)

If $\tan θ = - \frac{5}{12},$ then what can be the value of sin θ?

What is the value of $\cos^4\frac{7\pi}{8}+\cos^4\frac{5\pi}{8}?$