The sum of all interior angles of a regular polygon is twice the sum of all its exterior angles.  The number of sides of the polygon is

 If $$ {x=7-4\sqrt{3}}$$ find the value of $$ {\sqrt{x}+{1\over {\sqrt{x}}}}$$.

In a triangle ΔABC, the sides DE parallel to BC and AD = 6 cm, DB = 9 cm, AE = 8 cm, find the value of AC.

Two medians AD and BE of ∆ABC intersect G at right angle. If AD = 9 cm and BE = 6 cm, then the length of BD ( in cm ) is

If two complimentary angles are in the ratio of 4:5, find the greater angle.

The area of a circle is proportional to the square of its radius. A small circle of radius 3 cm is drawn within a larger circle of radius 5 cm. Find the ratio of the difference between the area of the larger circle and that of the smaller circle to the area of the larger circle.

In ΔABC, AB = AC and ∠B = 40 °, find the value of ∠A.