首先对函数式进行化简y=4cos x - 3sin^2 x + 2=4cos x - 3(1-cos^2 x )+ 2=4cos x - 3+3cos^2 x + 2=3cos^2 x+4cos x - 1令cosx=t，则y=3t^2+4t-1问题就转化成了当-1=<t<=1时，求y=3t^2+4t-1的最大值和最小值 下面再对y=3t^2+4t-1进行化简y=3t^2+4t-1=2t^2+4t+2+t^2-3=2(t^2+2t+1)+t^2-3=2(t+1)^2+t^2-3当-1=<t<=1时0<=t+1<=2 ∴0<=2(t+1)^2<=8 0<=t^2<=1...
