Investigation 7A: Is the Calculator Defective? & Investigation 7B: The Distance Formula and Compound Angle Identities
- The sine function is odd. Rotating the sine function 180° about the origin yields the same function. Thus, sin(-x) = -sinx.
- The cosine function is even. Reflecting the cosine function in the y-axis yields the same function. Thus, cos(-x) = cosx.