17．已知函数f(x)=2sinx−xcosx−xf(x)=2\sin x-x\cos x-xf(x)=2sinx−xcosx−x，f′(x)f\prime (x)f′(x)为f(x)f(x)f(x)的导数．（1）求曲线y=f(x)y=f(x)y=f(x)在点A(0A(0A(0，f(0))f(0))f(0))处的切线方程；（2）g(x)=x2−2x+a(a∈R)g(x)=x^{2}-2x+a(a\in R)g(x)=x2−2x+a(a∈R)，若对任意x1∈[0x_{1}\in [0x1∈[0，π]\pi ]π]，均存在x2∈[1x_{2}\in [1x2∈[1，2]2]2]，使得f(x1)>g(x2)f(x_{1})>g(x_{2})f(x1)>g(x2)，求实数aaa的取值范围．