Circles

Question 1

Circumference of circle

Answer 1

πd

Question 2

Arc length

Answer 2

°/360 x 2πr

Question 3

Circle Theorems

Answer 3

-Angles in semi circle meets circumference at 90°
-Angle at circumference = half of angle at centre
-Angle in same segment from common chord are equal
-Opposite angles in a cyclic quadrilateral = 180°
-Radius meets tangent at 90°
-Angle between chord and tangent are equal to the opposite angle in the triangle
-Radius through the midpoint of a chord meet at 90°

Question 4

Equation of a circle

Answer 4

x^2 + y^2 = r^2
(r being radius)