Pre-calc Idenities & math Help me understand this please

Ok I don't understand how to do these 3 types of questions.

Please help me** understand **how to do them. Thanks for your time.

1. Verify the identity (Can only change one side, and end result must equal each other)

cos^3Xsin^2X=(sin^2X-sin^4X)cosX

2. Sole the equation.

4cosX=1+2cosX

3. Find the exact values of the sine, cosine, and tangent of the angle by using the sum or difference formula.

345 degrees = 300 degrees + 45 degrees

Thanks for any help.