If the equation of the circle is (x-1)^2 + (y+3)^2 = 16 and the sector of the circle has a central angle of 90 degree. Its arc length is ( ? ) pi cm.

Answer 1

From equation of circle r² = 16 or r = 4. So length s of arc l = rθ = r π·90°/180° = 4·π/2 = 2π