So, I've been having issues with my homework. My teacher was gone for the class and posted up videos, but both the videos and the book don't really go over a number of the problems. I'm having issues with a few, and I was wondering if somebody could guide me through them step by step.

Anyways, here are the ones I was having problems with:
Find sin 2x, cos 2x, and tan 2x from the given information. csc x = 7, tan x < 0

Simplify the expression by using a Double-Angle Formula or a Half-Angle Formula.
a) cos2 θ/2 - sin2θ/2 b) 2 sin θ/2 cos θ/2

Evaluate the expression under the given conditions. sin 2θ; sin θ = 1/5, θ in Quadrant II

Find the value of the sum

cos π/12 + cos /12

Sorry it's quite a lot, but it's new information and I 'm having a hard time without a professor around to answer my questions.