在三角函数中,我们经常遇到一类形如“已知asin x+bcos x=c,求角x的某(些)三角函数值”的问题.解决这类问题的一般思路是:将条件式与sin~2x+cos~2x=1联立解方程组,求得sin x或cos x,再通过同角三角函数的关系式求得其它三角函数值.这种处理方法虽然思路清晰,但运算量较大,且涉及到开平方对正、负号的取舍,尤其是遇到限制了角 In trigonometric functions, we often encounter the problem of a certain kind of trigonometric function value “x” as known as asin x + bcos x = c, seeking angle x. "The general idea of ​​solving such problems is: The conditional expression and sin ~ 2x + cos ~ 2x = 1 set of simultaneous equations, find the sin x or cos x, and then by trigonometric trigonometric functions to obtain the other trigonometric functions. Although this approach clear idea , But a large amount of computation, and involves Kaiping square alignment, the choice of the negative sign, especially in the case of limited angle