Need assistance with Maths again

Hey again,

Yes i have some problems with questions about Trig. Functions again and im planning to make it a regular thing if posting on the forum is my last resort if you guys dont mind. Here are the questions:

  1. cos ( pi /4 + x ) is the identity of 1 / root 2 (cos x - sin x)

  2. cos (a + b ) . cos (a + b) is the identity of cos squared a - sin squared b

Can somebody assist me?