Product of slopes of two perpendicular lines= -1
True
If m1 and m2 be the slopes of two lines, θ be the angle between them
tanθ=∣∣m1−m21+m1m2∣∣
If θ=90∘
tan90∘=∣∣m1−m21+m1m2∣∣
Then θ=90∘tanθ is not defined
Denominator = 1+m1.m2=0
m1.m2=−1
So, gives statement is true.