The cosine rule can be rearranged so that it can be used to find an unknown angle. This time we need to enter into the formula the three side lengths only. All that remains is lots of practice!
On the calculator, enter 'Shift Cos' followed by the numbers and round to 2 decimal places.
Activity: Use your calculator to find the unknown angles below using the cosine angle rule.
ANSWERS: 1) 37.421 2) 63.26 3) 41.41