Helen Melon :)

This week we learned section 10-1.

Since you can't use your calculator, you would fail this section if you don't know your trig chart.

Formulas:

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

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


*To find the angle you are looking for you would add or subtract.

Examples 1: Find exact value of Cos 15 degrees.

alpha=45 beta=30

Cos(45-30)= cos 45 cos 30+sin 45 sin 30
=(sq. root 2/2)(sq.root 3/2) + (sq. root 2/2)(1/2)
ANS= sq.root 6 + sq.root 2/4

Examples 2: Simplify:

sin 20 degrees cos 15 degrees-cos 20 degrees sin 15 degrees
=sin(20-15)
ANS= sin 5 degrees.