1. Parallel and Perpendicular Lines
Coordinate Geometry
Parallel and Perpendicular Lines

2. PARALLEL x-axis l 2 units DOWN 4 units LEFT k 2 units DOWNm
2 units DOWN
4 units LEFT

3. Parallel Line All line that are parallel to each other have:
Same value of gradient.
No intersection point or the lines never meet except the lines are coincide to each other.

4. Exercise 1
State whether each of the following pair of gradients, m1 and m2 represents parallel lines or not.
m1 = 2, m2 = ½
m1 = 1, m2 = -1
m1 = 1.5 , m2 = 3/2
m1 = 4, m2 = 1/8
Which pair of these equations are parallel?
y = x – 2 , y = 2x + 8
2y = 2x – 4 , y = x – 3
4y = 3x – 1 , y = 4 + 3x

5. PARALLEL Word-Written Question
(-6, 6) k
2 units DOWN
4 units LEFT
x-axis
Word-Written Question
A line l that pass through point (-6,6) is parallel to a line k with equation y = (1/2)x + 4. Find the equation of line l.

6. PERPENDICULAR x-axis l m 2 units LEFT k 4 units UP 2 units DOWN

7. Perpendicular Line All line that are perpendicular to each other have:
Negative reciprocal value of gradient.
Example: ……………
Conclusion: …………….
One intersection point.

8. Exercise 2
State whether each of the following pair of gradients, m1 and m2 represents perpendicular lines or not.
m1 = 2, m2 = ½
m1 = 1, m2 = -1
m1 = 1.5, m2 = 3/2
Find the gradient of a line that is perpendicular to a line with gradient:
3/4
-2.5 -1
Which pair of these equations is perpendicular to each other?
y = 6 – 2x , y = x – 1
y = (x/3) – 2 , y = 4 – 3x
3y = 2x – 2 , y = 5 – (3/2)x

9. Word-Written Question
PERPENDICULAR l k
2 units DOWN
(4, 1)
4 units LEFT
x-axis
Word-Written Question
A line l that pass through point (4,1) is perpendicular to a line k with equation y = (1/2)x + 4. Find the equation of line l.

10. Congratulation!!! Don’t forget to play study at home.