Lesson 4: 5.4 Sum and Difference Formulas

How do you simplify expressions and solve equations that contain sums or differences of angles?

sum
difference
reduction formulas

HSF-TF.C.9 - Prove the addition and subtraction formulas for sine, cosine, and tangent and use them to solve problems.

Use Khan Academy resources.

Students will learn formulas that will allow them to solve trigonometric equations to solve trigonometric equations involving angles that are the sum or difference of special angles they have already studied.

You can use sum and difference formulas to rewrite trigonometric expressions. For instance, sum and difference formulas can be used to rewrite a trigonometric expression in a form that helps you find the equation of a standing wave.

Some students may use a calculator to give an answer that is a decimal approximation instead of writing the exact answer in radical form.

When using the sum and difference formulas, tell students that they can use any combination of special angles.

Use common assessments.

Pre-Calculus with Limits resources.