M - Pure 1 - 9) Trigonometric ratios

Question 1

Formula for cosine rule to find a missing side and angle

Answer 1

• a = √[b² + c² - 2bc·cos(A)]
• A = cos^-1[(b² + c² - a²) / 2bc]

Question 2

Formula for sine rule to find a missing side and angle

Answer 2

• a = [b / sin(B)] × sin(A)]
• A = sin^-1[(sin(B) / b) × a]

Question 3

Possible solutions of sine rule

Answer 3

• sin(θ)
• sin(180° - θ) → acute

Question 4

Formula for the area of a triangle

Answer 4

½ab·sin(C)