How do I find the missing length using trigonometry?

First of all, label the sides in the right-angled triangle. Then, write out SOHCAHTOA, using three small triangles. Next, tick off the letters of the sides that either have a number, or the letter x, written on them. This will tell you which trigonometry ratio to use. Once you have selected the trig ratio, cover up the letter of the side you are trying to find. This will tell you whether to multiply or divide. Enter the calculation in to your calculator. Don't forget to round or state units like the question has asked you to do.