在进行三角式的化简和求值时,常常遇到表达式中出现较多的相异的角.这时我们必须首先弄清这些角之间的相互关系,选定一个目标,其余的角都朝着这个目标转化,按题意配出相应的角的和与差、倍与半,创造使用三角公式的条件,以达到化简 In the triangulation reduction and evaluation, we often encounter many different angles in the expression. At this time we must first understand the relationship between these corners, select a goal, the remaining corners All of them are transformed towards this goal. According to the question, the sum of the corresponding angles is summed with the difference, the times and the half, and the conditions for using the trigonometric formulae are created to achieve simplification.