A unique circle can always be drawn through x number of given non-collinear points, then X must be 

ΔABC is an equilateral triangle in which D, E and F are the points on sides BC, AC and AB, respectively, such that AD ⊥ BC, BE ⊥ AC and CF ⊥ AB. Which of the following is true?

A line touches a circle of a radius 6 cm. Another line is drawn which is tangent to the circle. If the two lines are parallel then the distance between them is:

The area enclosed between the circumferences of two concentric circles is 45π square cm and their radii are in the ratio of 3:2. What is the area off the outer circle?

Given that (a²+b²)=60, then find the value of (a+b)²+(a–b)².

Each internal angle of regular polygon is two times its external angle. Then the number of sides of the polygon is: 

Given that DE || BC, AD : DB = 3 : 4, find out ar(∆ADE)/ar(∆ABC)?

If angle bisector of a triangle bisects the opposite side, then what type of triangle is it?