f(x)的定义域为 [-1,1],在 [-1,1]上单调递增
x=-1,f(x)的最小值为-π/4-π/4 = -π/2
x=+1,f(x)的最大值为π/4+π/4 = π/2
函数f(x)=arctanx+1/2arcsinx的值域是 [-π/2,π/2]