有些数学问题,如果从正面入手感到比较困难,比较繁琐,或者出现一些逻辑上的困境,这时,我们就要采取逆向思维.下面举例说明逆向思维在高中数学中的应用.1.由主元联想客元例1若方程cos2θ+6sinθ+a-2=0在θ∈[π/6,2π/3]时有解,求实数a的取值范围.解析原方程变形为2sin~2θ-6sinθ-a+1=0,这是关于sinθ的二次方程.利用二次函数 Some math problems, if it is more difficult, complicated, or some logical dilemma from the front, then we must take the reverse thinking.Examples of the application of reverse thinking in high school mathematics.From the main element Legendary guest element example 1 If the equation cos2θ + 6sinθ + a-2 = 0 in θ∈ [π / 6,2ππ / 3] have solution, find the real a range of values. Analysis of the original equation deformation 2sin ~ 2θ-6sinθ -a + 1 = 0, which is a quadratic equation with respect to sinθ, using a quadratic function