7.2 Addition and Subtraction Formulas
Ideas in this lesson
- Exact values with addition and subtraction formulas
- Recognizing and using the formulas in reverse
- Values of sin(s + t) from given information
- Cofunction identities and proofs with sums
Exact values with addition and subtraction formulas · Worked example
sin 15° = sin(45° − 30°) = ?
Answer: \frac{√6 − √2}{4}
\frac{√2}{2} · \frac{√3}{2} − \frac{√2}{2} · \frac{1}{2}.