10-1

today im showing you the formulas for cos (alpha +/- beta) and sin (alpha +/- beta). i will also show you an example on using them. the key word for this chapter is REPLACEING. this is because you are replacing things in the formulas. the first formula is cos (alpha +/- beta) = cos (alpha) cos (beta) -/+ sin (alpha) (beta). the next one is sin (alpha +/- beta) = sin (alpha) cos (beta) +/- cos (alpha) sin (beta).


EX: sin 75 cos 15 + cos 75 sin 15

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

sin(75+15)= sin 90 = 1