1. Straight Line Flashcards
2 forms of straight line equation
y = mx + c
(m is gradient, c is y intercept)
ax + by + c = 0
Gradient equation
m = y2 - y1 / x2 - x1
Gradient of line sloping up from left to right
+ive
Gradient of line sloping down from left to right
-ive
Gradient of a horizontal line
0
Gradient of a vertical line
Undefined
Lines with the same gradient are ______
parallel
Gradient of the line joining A (6,3) and B (3,8)
-5 / 3
Given the points C (2,p) and D (10,7) have a gradient of 1/4, find the value of p
p = 5
Requirements for collinearity
3 or more points on a straight line
Same gradient
Share a common point
3 or more points on a straight line
Same gradient
Share a common point
Requirements for collinearinity
Method for proving collinearity of A, B, and C
- Gradient AB
- Gradient BC
- Statement
Collinearity statement
Since mAB = mBC and share common point B, the points A, B and C are collinear
Are A (2,6), B (-1, 3) and C (3,8) collinear?
Not collinear as mAB ≠ mBC
tan0 =
Gradient, y2 - y1 / x2 - x1
What can be found with tan0 = m
If gradient is known, angle can be found
If angle is known, gradient can be found
If gradient is known, angle can be found
If angle is known, gradient can be found
m = tan0
Angle from triangle of straight line e =
Angle the straight line makes with x axis
Negative on bottom and top of fraction
Becomes positive as it cancels out
Calculate the size of the angle of the line joining P (3,9) and Q (-2, 1)
Gradient = 8 / 5
Angle = 57.99 °
How to find the distance between two known points
By constructing a right angle triangle
Distance formula
Find the distance between A (5,7) and B (-8, 2)
13.93
Rearrange 3x -2y = -7 and find a, b, and c
3x - 2y + 7 = 0
a = 3
b = -2
c = 7
rearrange y = -5x + 9 and find a b and c
5x + y - 9 = 0
a = 5, b = 1, c = -9
Rearrange to the general equation and find the values of a, b, and c:
y - 2 = 3/4 (x + 5)
-3x + 4y - 23 = 0
a = -3, b = 4, c = 23