F3 Trigonometry(easy)

1.it is given that sinθ=1/4.find the value of 2sin^2θ-cos^2θ without using a calculator

2.it is given that tan(90-θ)=1/5.find the value of sin(90-θ)+sinθ/cos(90-θ)tanθ by using trigonometric identities

3.Prove that sin^2θ+(1-cosθ)^2=2(1-cosθ) is an identity


4.prove that 1-2sinθcosθ=(cosθ-sinθ)^2 is an identity