What is the area (in cm²) of the circumcircle of a triangle whose sides are 6 cm, 8 cm and 10 cm respectively?

In a polygon, the sum of the interior angles is double the sum of the exterior angles. What is the number of sides of the polygon?

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

If the ratio of the measurements of the three angles of a triangle is 2: 3: 4, then the measurement of its largest angle is.

If one angle is half of its complementary angle, find that angle.

If ABC is an equilateral triangle and P, Q, R respectively denote the middle points of AB, BC, CA, then 

If ABCDEF is a regular hexagon, then what is the value (in degrees) of ∠ADB?