10-1

Today I'm going to do my blog on chapter 10 section 1. This section is on the sums and difference for sine and cosine. This invloves six different formulas. The formulas are:

cos (alpha +/- beta) = cos (alpha) cos (beta) -/+ sin (alpha) (sin beta)

sin (alpha +/- beta) = sin (alpha) c0s (beta) +/- c0s (alpha) sin (beta)

sin x + sin y = 2 sin (x+y/2) cos (x-y/2)

sin x - sin y = 2 cos (x=y/2) sin (x-y/2)

cos x + cos y = 2 cos (x+y/2) cos (x-y/2)

cos x - cos y = -2 sin (x+y/2) sin (x-y/2)

Here are some examples!!!

Simplify: sin (65 degrees) cos( 25 degrees) + cos (65 degrees) sin (25 degrees)

= sin (65 degrees + 25 degrees)

= sin 90 degrees

= 1

Simplify: cos ( 180 degrees) cos (120 degrees) + sin (180 degrees) sin (120 degrees)

= cos (180 - 120)

=sin 60 degrees

= 1/2

Well. there you go!

-Dana (: