Start with: sin 39° = opposite/hypotenuse sin 39° = d/30 Swap Sides: d/30 = sin 39° Use a calculator to find sin 39°: d/30 = 0.6293 Multiply both sides by 30: d = 0.6293 x 30 d = 18.88

We can use the sine rule when we're given the sizes of: two sides and one angle (which is opposite to one of these sides) one side and any two angles Example Find the size of angle R. \