This video shows the method to prove some trigonometric identities. This involves the use of algebra and knowledge of basic trigonometric identities. The video demonstrates three examples to illustrate this problem and its solution. The first problem shows a relatively simple problem involving sines and cosines. The video shows some basic algebra steps to simplify the problem and prove the identities. The second example involves a slightly complicated problem involving square of combination of terms containing sines and cosines. In this example the square term is broken so that the identity is proved. The identities proved in the previous examples are used in the third example.