Learning Resources

Investigation 7A: Is the Calculator Defective? & Investigation 7B: The Distance Formula and Compound Angle Identities

Part (a)

To develop the identity for cos(a + b), you will use the following facts:

• cos(a - b) = cosa cosb + sina sinb

• cos(a + b) = cos(a - (-b))

• cos(b) = cos (-b)

• sin(-b) = -sinb