The sum of all interior angles of a regular polygon is 10507, What is the measure of its each exterior angle ?

​a, b and c are the sides of a right triangle with c as hypotenuse. The radius r, of the circle which touches the three sides of the triangle is :

Which of the following statements is correct?

1. The angle between two tangents to a circle may be 0°.

2. If a transversal intersects two lines such that a pair of alternate interior angles is equal, then the two lines are parallel.

3. The tangents at the end points of a diameter of a circle are perpendicular.