cartesian plane

proview · #1 $Old$ 11-16-2008, 06:06 PM

find the radius of a circle with center at (-2, 1), if a chord length of 10 is bisected at (-3, 0).

can you help me with this one? i think ill know how to solve it if i know the drawing.

by the way, answer is 3┌3 or 5.196 according to our prof.

Jhevon · #2 $Old$ 11-16-2008, 08:55 PM

Quote:

Originally Posted by proview $View Post$

find the radius of a circle with center at (-2, 1), if a chord length of 10 is bisected at (-3, 0).

can you help me with this one? i think ill know how to solve it if i know the drawing.

by the way, answer is 3┌3 or 5.196 according to our prof.

yes, that's the answer. i wish i had my graphing software and stuff on this PC so that i could show you the diagram.

anyway, plot the center, and draw a line connecting it to (-3,0). the chord is perpendicular to this line. so draw that (the line you drew first is the perpendicular bisector of the chord). then use the formula $\text{chord length} = 2 \sqrt{r^2 - d^2}$ , with $r$ and $d$ as shown here. you can figure out the value of d using Pythagoras' theorem, and then just solve the equation for r

proview · #3 $Old$ 11-17-2008, 07:29 AM

thanks for help. i got the drawing and realized that you can use Pythagorean theorem to solve it all the way.