Circle Theorem: Chord of a Circle, Theorem 1, Theorem 2, Theorem 3, Theorem 4, Theorem 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

Glide to success with Doorsteptutor material for IFS : fully solved questions with step-by-step explanation- practice your way to success.

Circle Theorem: Theorem 4, Theorem 5

(4) To any point on the circumference of the circle, the measure of the angles subtended from the same arc is equal to half of the angle subtended at the center by the same arc.

To Any Point on the Circumference of the Circle

From the above given figure,

Join passing through


Since angles opposite to equal sides of a triangle are equal,

By exterior Angle Property of the triangle, we have

Thus, from equation (ii) and (iii) , we have

Similarly, in ,

Exterior angle,

From equation (iv) and (v) , we have

, Hence Proved

(5) The opposite angles in a cyclic quadrilateral are supplementary.

The Opposite Angles in a Cyclic Quadrilateral Are Supplement …


Let us consider arc .

using theorem (4)

For arc ,

Reflex using theorem (4)

From (i) and (ii) , we get