Episode 9 — 2D & 3D Trigonometry

Reduction Formulae

Learners will be able to:

• Identify angles that can be written as 90 degrees plus or minus theta, or 180 degrees plus or minus theta, or 360 degrees plus or minus theta. • Explain the purpose of reduction formulae in simplifying expressions and finding numerical values of trigonometric functions of angles greater than 90 degrees. • Describe how to relate a sine graph to the quadrants on the Cartesian plane to determine the signs of different ratios of sine theta. • Identify co-functions, such as sine of 90 minus theta being equal to cos of theta, in the first quadrant. • Apply reduction formulae to simplify expressions and find numerical values of trigonometric functions in different quadrants.