analytic geometry

14041471 · #1 $Old$ January 6th, 2009, 02:10 PM

i need to find the distance between these two points on a graph (1,3) and (-2,7)

its a multiple choise question and the options are, sqrt of 5, 25,7 and 5

soely on instinct, i beleive the awnser is 7, but i don't actuallyk now the formula to check it. so any help would be much appreciated.

craig · #2 $Old$ January 6th, 2009, 02:17 PM

Call the points $(a, b)$ and $(c, d)$ .

The distance between the points is simply $\sqrt{(c-a)^2+(d-b)^2}$ .

This is just pythagoras, making a right angle triangle and finding the lenght of the hypotenuse.

Hope this helps

Craig

bigb · #3 $Old$ January 6th, 2009, 02:19 PM

Quote:

Originally Posted by 14041471 $View Post$

i need to find the distance between these two points on a graph (1,3) and (-2,7)

its a multiple choise question and the options are, sqrt of 5, 25,7 and 5

soely on instinct, i beleive the awnser is 7, but i don't actuallyk now the formula to check it. so any help would be much appreciated.

USe the distance formula: sqrt{(x2-x1)^2+(y2-y1)^2}
sqrt{(-2-1)^2+(7-3)^2}
sqrr{9+16)
5: the answer is 5