This is a good question. Here's a proof I just came up with that the angle addition formula for sin () applies to angles in the second quadrant: Given: pi/2 < a < pi and pi/2 < b < pi // a and b are obtuse …

Sal reviews 6 related trigonometric angle addition identities: sin (a+b), sin (a-c), cos (a+b), cos (a-b), cos (2a), and sin (2a). Created by Sal Khan.

Given the sum of a pair of angle measures and the algebraic expressions that represent them, form and solve an equation. Includes complementary, supplementary, and other adjacent angles.

Then we use transversals, vertical angles, and corresponding angles to rearrange those angle measures into a straight line, proving that they must add up to 180°.

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Review the basics of complementary and supplementary angles, and try some practice problems.

In this topic, we will learn what an angle is and how to label, measure and construct them. We will also explore special types of angles.

Learn about complementary and supplementary angles, as well as the definitions of adjacent and straight angles.

The pink and blue angles add up to 180 ∘ because they are adjacent and form a straight line.

Supplementary angles add up to 180 degrees and complementary angles add up to 90 degrees.