Find the length of AB from the right-angle triangle ABC. Angle ACB = 40 degrees and side BC = 15cm.

Label each of the sides using the angle BCA. Therefore, AC = Adjacent, BC = Hypotenuse and AB = Opposite. Use the anagram SohCahToa to identify the side that we have (BC) and the side we are looking for (AB). After ticking the letters of SohCahToa, we will now use the Sin fraction. Let Sin(40) = Opposite / Hypotenuse. Replace Opposite and Hypotenuse with x and 15. Sin(40) = x/15. To solve this equation, multiply both sides by 15. 15 Sin(40) = x. Calculate this figure using your calculator to find the Opposite side AB. The answer is 9.64 cm (2 decimal places).