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The Distance and Midpoint Formulas!. To be used when you want to find the distance between two points or the midpoint between two points. You have learned…. 1 The Pythagorean a c Theorem a 2 + b 2 = c 2 b 2
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The Distance and Midpoint Formulas! To be used when you want to find the distance between two points or the midpoint between two points
You have learned… 1 The Pythagorean a c Theorem a2 + b2 = c2 b 2 When we are finding c we are really finding the distance between angles 1 and 2 If we solve for c we get c = √(a2 + b2) This is how the distance formula is derived – it is useful when we know coordinates
The Distance Formula! The distance formula is d = √((y2 – y1)2 + (x2 – x1)2) And is used to find the distance between two points on the coordinate plane Let’s practice one!
Example: What is the distance between (2, -6) and (-3, 6)? First, identify x1, y1, x2 and y2 x1 = 2 y1 = -6 x2 = -3 y2 = 6 Now, we use the formula: d = √((6 – -6)2 + (-3 – 2)2) = √(122 + (-52)) d = 13
The Midpoint Formula! The midpoint formula is used to find the coordinate that is the exact midpoint between two other coordinates The x-coordinate of the midpoint is found by (x2 + x1)/2 The y-coordinate of the midpoint is found by (y2 + y1)/2 So, the coordinate of the midpoint is: (x2 + x1)/2, (y2 + y1)/2
Example: What is the coordinate of the midpoint between (1, 2) and (-5, 6)? Again, identify x1, y1, x2 and y2 x1 = 1 y1 = 2 x2 = -5 y2 = 6 Now use the formula: x-coordinate: (1 + -5)/2 = -2 y-coordinate: (2 + 6)/2 = 8 So, the midpoint is located at the coordinate (-2, 8)
Another Example On the coordinate plane, it is given that the midpoint of points A and B is (5, 7). If point A is located at (-1, 2), where is point B located? In this case, we know the midpoint and the coordinate of point A. In a sense, we need to work backwards. Let’s define what we have:
x1 = -1 y1 = 2 x2 = ? y2 = ? So we know… (-1 + x2)/2 = 5 (2 + y2)/2 = 7 -1 + x2 = 10 (2 + y2) = 14 x2 = 11 y2 = 12 So the coordinate of point B is (11, 12)