Triangle ABC Angle A = 74° a = 126 b = 84 Use the sine rule \(\frac{a}{sin A} = \frac{b}{sin B}\) Plug in the given \(\frac{126}{sin(74)} = \frac{84}{sin(B)}\) Cross multiply 126 × sin(B) = 84 × sin(74) Divide by 126 \(\frac{126sin(B)}{126} = \frac{84sin(74)}{126}\) 126 and 126 cancels out sin(B) = \(\frac{84sin(74)}{126}\) take sin inverse (\(sin^{-1}\)) B = \(sin^{-1}\) (\(\frac{84sin(74)}{126}\)) B = 39.85° = 39.9°
