Consider the right angled triangle with vertices labelled a, b, c. Angle A = 60°, Angle B = 90°, length ab=4cm, length ac=xcm. If cos60° = 0.5, work out the value of x.

The first thing to do in such a question is to draw out the information you have been given. Not only does this help to process the question again, so that no vital information is missed, but also makes it a lot easier to see how to go about solving the problem.The trigonometric rule of 'SOH-CAH-TOA' can then be applied. My useful hint to remember this is 'Silly Old Hitler, Caused Awful Havoc, Too Our Armies'In this question we are given information on the Cosine, Adjacent and Hypotenuse. Therefore 'CAH' is the part we need. (Cos60° = adjacent/hypotenuse) When we sub in the values given, we see 0.5=4/x, which can be rearranged to x= 4/0.5, so x=8cm.