the radius of a circle is 4, the radians in pi/2.whats the arc length?

Answer 1

For a circle with radius 4, the total circumference is 2*pi*r, or 8pi. Now if you're looking at only an arc that covers pi/2 of the circle, you're really looking at 1/4 of the total circumference (the whole circle sweeps 2pi). So the arc length you're looking for is 8pi/4, or 2pi.