6.cos330°=cos(360º-30º)=cos30º=√3/2
7.cos(π+α)=-1/2 ==>cosα=1/2
∵3π/23x0²+1=4 ==>x0=±1
x0=1 ,f1)=0,P0(1,0)
x0=-1,f(-1)=-4 ,P0(1,-4)
P0(1,0),P0(1,-4)均符合题意
答案：D.(1,0)或(-1,-4)
9.函数f(x)=(x-3)e^X的单调递增区间是多少?
f'(x)=e^x+(x-3)e^x=(x-2)e^x
f'(x)>0 ==>x>2;f'(x)x