Mathematics for IGCSE & O level - Angles (Section 2 - No. 7)
If two lines intersect and form an angle of 90 degrees, what can we say about the lines?
They are parallel.
They are perpendicular.
They are skew.
They are intersecting, but not special.
คำอธิบาย
Lines intersecting at a 90° angle are perpendicular.