★★★★追30,★★★★已知直线2x+y-2=0和mx-y+1=0的夹角为π/4,那么m的值为?

Question

★★★★追30,★★★★
已知直线2x+y-2=0和mx-y+1=0的夹角为 π/4,那么m的值为?

Answer 1

直线l1:2x+y-2=0 l2:mx-y+1=0
l1的倾斜角为A,则tanA=-2
l2的倾斜角为B,则B=A±π/4
由诱导公式tanB=-1/3或3
则m=tanB=-1/3或3