How many diagonals can be drawn by joining the vertices of an octagon?
20
Concept used :
Number of diagonals in polygon = [n(n - 3)]/2 (where n is the number of sides)
Calculations :
Here n will be 8 as octagon has 8 sides.
Number of polygons in octagon = [8 × (8 - 3)]/2
⇒ (8 × 5)/2
⇒ 40/2 = 20
∴ Option 1 will be the right choice.
Important Questions from Quadrilaterals
The ratio between the length and breadth of a rectangular park is 3 : 2. If a man cycling along the boundary at the speed of 12 km per hour completes one round in 8 minutes, then the area of the park in square meter will be
The side of a rhombus is 26 cm. The length of one of its diagonals is 20 cm. The sum of the lengths of the diagonals of this rhombus is equal to the perimeter of a rectangle. If the difference between the length and breadth of the rectangle is 6 cm, then what is the area of the rectangle?
PQRS is a cyclic quadrilateral. If ∠P is 4 times ∠R, and ∠S is 3 times ∠Q, then the average of ∠Q and ∠R is:
ABCD is a trapezium in which AB || DC and DC is perpendicular to BC. If ∠DAB = 110°, then ∠ABC - ∠ADC =_____.
The adjacent angles of a rhombus are in the ratio of 3 : 6. The smallest angle of the rhombus is:
