Find the Missing Angle Worksheets

How to Find the Measure of Angles of a Triangle When You Know the Length of the Sides - More often students are confused when they are finding unknown values of a triangle. For instance, finding the angles when all the sides are given. Well, the case is that you must be able to know the formulas and then just put the values at their respective places and there is no double you are going to get the values you are looking for. However, there are certain steps that are involved which are as follows. If you have a three-sided polygon (a triangle) and you know the side lengths, then the figure is rigid and it should be possible to find the angles. If you have a polygon with more than three sides and you know the side lengths, then the figure is not rigid, and the angles can vary. The relationship you are looking for is called the Law of Cosines. I can show you a proof at least for an acute triangle. If the triangle is not acute you have to modify my proof slightly. You also need to break the triangle into two right angled triangles to help you get the procedure using Pythagoras theorem.