- #1
viet_jon
- 131
- 0
Homework Statement
cos(a+b)
Homework Equations
find formulas for above
The Attempt at a Solution
cos (a+b)
= cos (a-(b))
=cos(a)cos(-b) + sin(a)sin(-b)
=cos(a)cos(b) - sin(a)sin(b)
I been scratching my head at this for hours now, and I still can't figure out how this works.