Trigonometry (Grade 12 NSC Matric Mathematics): Flashcards

Expressions involving sum or difference of two angles

Does NOT apply: $\cos(\alpha - \beta) \neq \cos \alpha - \cos \beta$

$\cos \alpha \cos \beta + \sin \alpha \sin \beta$

$\cos \alpha \cos \beta - \sin \alpha \sin \beta$

$\sin \alpha \cos \beta - \cos \alpha \sin \beta$

$\sin \alpha \cos \beta + \cos \alpha \sin \beta$

Sign matches the angle operation (+ stays +, - stays -)

Sign opposite to angle operation (+ becomes -, - becomes +)

$\sin \theta$

$45° + 30°$