Important Formulae:1. Circumference of a circle = 2 Π r.
2. Area of a circle = Π r²
3. Length of an arc of a sector of a circle with radius r and angle with degreemeasure θ isθ/360× 2 Πr
4. Area of a sector of a circle with radius r and angle with degrees measure θ is 2360/θ× Πr²
5. Area of segment of a circle= Area of the corresponding sector Area of the corresponding triangle.
an = a + (n 1) d.
Sn =n/2[2a + (n 1) d ]
PQ = root (x2 - x1)² + (y2 - y1)²