Question

設直線l₁：x-2y+2=0的傾斜角為a₁，直線l₂：mx-y+4=0的傾斜角為a₂，且a₂=a₁+90°，則m的值為______．

Answer 1

∵a₂=a₁+90°
∴tana₂=tan（a₁+90°）=-

1

tanα1

∴tanα₁tanα₂=-1
∴

1

2

×m=-1
∴m=-2
故答案是-2．