Question 15: In the given figure, is the diameter of the circle with center . If , find .

Answer:

subtends at the center and at the circumference of the circle.

Question 16: In a Cyclic-quadrilateral . Sides and produced meet at point whereas sides and produced meet at point . lf ; find and .

Answer:

Given is a cyclic quadrilateral.

  or if , then

(sum of the opposite angles in a cyclic quadrilateral is )

In

… … … (i)

In

Therefore   … … … (ii)

Hence

Therefore 

Question 17: In the following figure, is the diameter of a circle with center and is the chord with length equal to radius . If produced and produced meet at point ; show that .

Answer:

Given: is diameter,

In

is equilateral

Therefore

In

(radius of the same circle)

Therefore

Similarly in

(radius of the same circle)

Therefore

Since is cyclic quadrilateral

Therefore (opposite angles of a cyclic quadrilateral are supplementary)

In

. Hence proved.

Question 18: In the following figure, is a cyclic quadrilateral in which is parallel to . If the bisector of meets at point and the given circle at point , prove that: (i) (ii)

Answer:

Given: is a cyclic quadrilateral

is the angle bisector) … … … (i)

(i) (alternate angles) … … … (ii)

In

Using (i) and (ii) we get 

(vertically opposite angles)

is a cyclic quadrilateral)

Also

(ii) subtends on circumference

subtends on circumference

Given

Therefore  (equal arcs subtends equal angles on circumference)

Question 19: is a cyclic quadrilateral. Sides and produced meet at point ; whereas sides and produced meet at point . If , find the angles of the cyclic quadrilateral .

Answer:

Given

In

In

or

Therefore

Question 20: In the following figure shows a circle with as its diameter. If and , find the perimeter of the cyclic quadrilateral . [1992]

Answer:

Given:

Therefore the perimeter of

Question 21: In the following figure, is the diameter of a circle with center . If , prove that: (i) (ii) is bisector of . Further, if the length of , find : (a) (b) .

Answer:

Given:

Consider and

is common

(angles in semi circle)

Therefore 

(i) (corresponding parts of congruent triangles)

(ii) (equal chords subtend equal angles on the circumference of the same circle)

Therefore bisects

Question 22: In cyclic quadrilateral ; and ; find: (i) (ii) (iii) (iv)

Answer:

Given and 

(angles in the same segment)

(angles in the same segment)

(opposite angles in a cyclic quadrilateral are supplementary)

Therefore

Question 23: In the given figure and ; find the values of and . [2007]

Answer:

Given and

(ABDE is a cyclic quadrilateral)

(straight line)

In :

Therefore

Therefore is a cyclic quadrilateral)

In :

Question 24: In the given figure, and . Find (i) (ii) (iii)

Answer:

Given and . Also

Therefore (alternate angles)

Hence

Therefore

and

Therefore

In :

Therefore

(angles in the same segment)

Question 25: is a cyclic quadrilateral of a circle center such that is a diameter of the circle and the length of the chord is equal to the radius of the circle. If and produced meet at , show that .

Answer:

Given

In :

In (Radius of the same circle)

Let

Therefore  … … … (i)

In (Radius of the same circle)

Let

Therefore  … … … (ii)

Now, (straight line angle)

In :

Question 26: In the figure, given alongside,