In △ ABC, DE // BC, AD = a, DB = b and BC = x, then, DE is equal to :

1. $\dfrac{a + b}{ax}$

2. $\dfrac{a + b}{a}$

3. $\dfrac{ax}{a + b}$

4. $\dfrac{a}{a + b}$

A kite shaped card-board is rotated about its line of symmetry (shown by dotted line). The solid figure so obtained has :

(i) one cone formed

(ii) two cones formed

(iii) three cones formed

1. only (ii)

2. only (iii)

3. both (i) and (iii)

4. neither (i) nor (iii)

The orthocenter, incenter, circumcentre and centroid of a triangle coincide, the triangle is :

1. scalene

2. isosceles

3. equilateral

4. right angled

If PT is tangent to the circle at point T and PAB is secant of this circle. Then which of the following statements is true ?

1. PT² = PA × AB

2. PT² = TB × PA

3. PT² = PA × PB

4. PT² = PB × TB