True or false: reading the identities

Exercise and reference answers

Questions

1. Statement is true

   Yes

   Statement

   The Pythagorean identity lets you find cos from sin.

2. Statement is true

   Yes

   Statement

   The sum formulae let you expand cos(x + y).

3. Statement is true

   Yes

   Statement

   Periodicity means adding 2π leaves the value unchanged.

4. Statement is true

   No

   Statement

   Every trigonometric identity holds only for acute angles.

5. Statement is true

   Yes

   Statement

   Radian measure is proportional to degree measure.

Explanation