14. DOUBLE-ANGLE and HALF ANGLE IDENTITIES
Double Angle Formulas Half Angle Formulas The + or – depends in which quadrant the original given value exists
Two types of double angle problems 1. verify/simplify 2. given a trig value find values of double angles
Type 1
Simplify
Simplify
Simplify
Simplify
Verify the identity
Verify the identity
Prove
Type 2
Let's draw a picture. 5 4 -3
Let's draw a picture. 1 4
Half Angle
Ex: Use the half angle formula to find the exact value of sin(105o) 105 exists in the II, so sine is positive! 2. Double 105 to get the numerator 3. Plug into the half formula 4. 5. Simplify
Find the exact value of the function.