David

section 10.1 with NO CALCULATORS

everybody else explained the hard part, so i'll go ahead and explain the easier part.
formulas: cos(α+/-β) = cos(α)cos(β) -/+ sin(α)sin(β)
sin(α+/-β) = sin(α)cos(β )+/- cos(α)sin(β)

You change the sign for cos.

Example:
they will give a satanic equation such as
sin75cos15+cos75sin15
and they as you to simplify
you look at the type of formula, and you can tell that you need the sin one
you use the numbers and put them in on the other side of the equation
so you would put sin(75+15) ( alpha + beta) and that equals sin90, which is pie/2 which is also 1, i'm not sure which on to put but yea. and its that easy

Example 2:
its the same process except they give you the other side of the equation

cos( pie + x) = -cosx
and you have to prove
you just take the first part of the equation and put it in the cos equation
pie is alpha and x is beta
after you complete this , if you've done it right, you will be proving the answer they have already given you
amen.