Double-Angle and Half-angle Formulas
Double-Angle Formulas
Finding exact values
Solutions
Solutions
solutions
Establishing Identities Develop a formula for sin (3θ) in terms of sin θ and cos θ.
Other variations of double-angle formulas
Establishing an identity Write an equivalent expression for cos^4θ that does not involve any powers of sine or cosine greater than 1.
Solution
Half angle formulas
Finding Exact Values Find the exact value of cos (15 degrees) Find the exact value of sin (165 deg) Find the exact value of tan (195 deg)
Finding Exact Values Remember to be careful to check the sign of the cosine of the angle Remember to look at the quadrant to determine if the final answer is positive or negative
Finding Exact Values
Solutions
alternative formula
On-line help Tutorial Video Help