A circle has a center at (1 ,2 )(1,2) and passes through (4 ,2 )(4,2). What is the length of an arc covering pi /4 π4 radians on the circle?

1 Answer
Jan 23, 2016

I found 28.328.3 units but have a look at my method.

Explanation:

I would first find the radius rr as the distance between the center and your given point:
r=sqrt((x_2-x_1)^2+(y_2-y_1)^2)=sqrt((4-1)^2+(2-2)^2)=sqrt(3^2+0^2)=3r=(x2x1)2+(y2y1)2=(41)2+(22)2=32+02=3

Then I would consider that the length ss of an arc of angle thetaθ (in radians) will be:
s=r*thetas=rθ
so that:
s=3*pi/4=3/4*3.14=28.27~~28.3s=3π4=343.14=28.2728.3 units