Tricky Circles (Mistake Fixed)

Geometry Level 2

The points (4, 7) and (2, 9) are the endpoints for the radius of a circle. Find the area of the circle divided by 2 π 2\pi .

128 32 64 4

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

3 solutions

The distance between two points is given d = ( x 2 x 1 ) 2 ( y 2 y 1 ) 2 d=\sqrt{(x_2-x_1)^2(y_2-y-1)^2} . So the length of the radius of the circle is r = ( 4 2 ) 2 + ( 7 9 ) 2 = 4 + 4 = 4 ( 2 ) = 2 2 r=\sqrt{(4-2)^2+(7-9)^2}=\sqrt{4+4}=\sqrt{4(2)}=2\sqrt{2} . Finally, the value of Area 2 π = π ( 2 2 ) 2 2 π = \dfrac{\mbox{Area}}{2 \pi}=\dfrac{\pi (2\sqrt{2})^2}{2 \pi}= 4 \color{#3D99F6}\boxed{\large 4}

By the distance formula , we get

r = ( 4 2 ) 2 + ( 7 9 ) 2 = 2 2 r=\sqrt{(4-2)^2+(7-9)^2}=2\sqrt{2}

The area of the circle is π ( 2 2 ) 2 = π ( 4 ) ( 2 ) = 8 π \pi (2\sqrt{2})^2=\pi (4)(2)=8 \pi . Dividing the area by 2 π 2 \pi , we get an answer of 4 \color{#D61F06}\boxed{\large 4} .

Timothy Cho
Jul 23, 2017

It should be correct this time....

Solution: Find the length of the radius: ( 4 2 ) 2 + ( 7 9 ) 2 = 8 \sqrt{(4-2)^2+(7-9)^2}=\sqrt 8 . Then find the area of the circle: A = π r 2 = π × 8 2 = 8 π A=\pi r^2=\pi\times\sqrt 8^2=8\pi . Divide by 2 π 2\pi and get 4 4

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...