Double and Half Angle Formulas Dr. Barry Shildneck Fall, 2014
Double Angle Formulas Given that you know the sum and difference formulas, derive a formula for the Sine, Cosine, and Tangent of twice an angle.
Double Angle Formulas Note: The sign of the value of the double angle is taken care of by the formula.
Example 1 sin(2θ) cos(2θ) tan(2θ) csc(2θ) cot(2θ) Use the triangle to determine the Values of each of the following. sin(2θ) cos(2θ) tan(2θ) csc(2θ) cot(2θ)
Example 2 Find the values of the sin2x, cos2x, and tan2x given
Example 3 Use identities to rewrite each expression in terms of a single trigonometric function. 1) 4sinxcosx 2) 5–10cos2x
Example 4 Derive a triple angle formula for the sine. Your final answer should be written in terms of the sin(x) only.
Half Angle Formulas
Example 5 Use the half-angle formula to find the exact value of the sin105o.
Example 6 Use the half-angle formula to find the exact value of the sin112.5o.
Example 7 Given , find the value of .