Answer:
The coordinates of C are (5 , 2)
The slope of CD is 3
The coordinates of D are (6 , 5) and (4 , -1)
Step-by-step explanation:
* Now lets study the problem
- The ends points of line AB are A = 2 , 3) and B = (8 , 1)
- CD is the perpendicular bisector of AB, and C lies on AB
- That means:
# C is the mid-point of AB
# The slope of AB × the slope of CD = -1 (one of them is a multiplicative
inverse and additive inverse of the other)
-Ex: the slope of one is a/b, then the slope of the other is -b/a
* The mid-point between two points (x1 , y1) and (x2 , y2) is:
[(x1 + x2)/2 , (y1 + y2)/2]
∵ C is the mid-point of AB
∴ C = [(2 + 8)/2 , (3 + 1)/2] = [10/2 , 4/2] = (5 , 2)
* The coordinates of C are (5 , 2)
- The slope of a line passing through points (x1 , y1) and (x2 , y2) is:
the slope = (y2 - y1)/(x2 - x1)
∴ The slope of AB = (1 - 3)/(8 -2) = -2/6 = -1/3
∵ CD ⊥ AB
∴ The slope of CD × the slope of AB = -1
∴ The slope of CD = 3
* The slope of CD is 3
- The length of a line passing through points (x1 , y1) and (x2 , y2) is:
the length = √[(x2 - x1)² + (y2 - y1)²]
∵ The length of CD = √10
∵ Point D is (x , y)
∴ (x - 5)² + (y - 2)² = (√10)²
∴ (x - 5)² + (y - 2)² = 10 ⇒ (1)
∵ The slope of CD is (y - 2)/(x - 5) = 3 ⇒ by using cross multiply
∴ (y - 2) = 3(x - 5) ⇒ (2)
- Substitute (2) in (1)
∴ (x - 5)² + [3(x - 5)]² = 10 ⇒ simplify
* [3(x - 5)]² = (3)²(x - 5)² = 9(x - 5)²
∴ (x - 5)² + 9(x - 5)² = 10 ⇒ add the like terms
∴ 10(x - 5)² = 10 ⇒ ÷ 10 both sides
∴ (x - 5)² = 1 ⇒ take √ for both sides
∴ x - 5 = ± 1
∴ x - 5 = 1 ⇒ add 5 to both sides
∴ x = 6
* OR
∴ x - 5 = -1 ⇒ add 5 to both sides
∴ x = 4
- Substitute the values of x in (2)
∴ y - 2 = 3(6 - 5)
∴ y - 2 = 3 ⇒ add 2
∴ y = 5
* OR
∴ y - 2 = 3(4 - 5)
∴ y - 2 = -3 ⇒ add 2
∴ y = -1
* The coordinates of D are (6 , 5) and (4 , -1)
