Question

导数 (28 9:56:56)已知曲线f(x)=x²在P点处的切线与直线3x-y+1=0的夹角为45°,则点P

Answer 1

f'(x)=2x

P(p,p^2)

l1与l2的夹角为θ,则tanθ=|(k2- k1)/(1+ k1k2)|

k2=3 k1=p

1=|(3-p)/(1+p*3)|

(3-p)/(1+p*3)=1 p=1/2

(3-p)/(1+p*3)=-1 p=2

P1(1/2,1/4) P2(2,4)