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State exterior angle theorem.

The sum of two angles of a triangle is equal to its third angle. Determine the measure of the third angle.

In the given figure, if AB || CD, EF || BC, ∠BAC = 65° and ∠DHF = 35°, find ∠AGH.

In ΔABC, if bisectors of ∠ABC and ∠ACB intersect at O at angle of 120°, then find the measure of ∠A.

If the side BC of ΔABC is produced on both sides, then write the difference between the sum of the exterior angles so formed and ∠A.

In the given figure, side BC of ΔABC is produced to point D such that bisectors of ∠ABC and ∠ACD meet at a point E. If ∠BAC = 68°, find ∠BEC.

Mark the correct alternative in each of the following:
If all the three angles of a triangle are equal, then each one of them is equal to

If two acute angles of a right triangle are equal, then each acute is equal to

An exterior angle of a triangle is equal to 100° and two interior opposite angles are equal. Each of these angles is equal to

If one angle of a triangle is equal to the sum of the other two angles, then the triangle is

Side BC of a triangle ABC has been produced to a point D such that ∠ACD = 120°. If ∠B = \[\frac{1}{2}\]∠A is equal to

In ΔABC, ∠B = ∠C and ray AX bisects the exterior angle ∠DAC. If ∠DAX = 70°, then ∠ACB =

In a triangle, an exterior angle at a vertex is 95° and its one of the interior opposite angle is 55°, then the measure of the other interior angle is

If the sides of a triangle are produced in order, then the sum of the three exterior angles so formed is

An exterior angle of a triangle is 108° and its interior opposite angles are in the ratio 4 : 5. The angles of the triangle are

In the given figure, ΔABC is an equilateral triangle. Find m∠BEC. 

In the given figure, ΔPQR is an isosceles triangle with PQ = PR and m ∠PQR = 35°. Find m ∠QSR and m ∠QTR.

In the given figure, O is the centre of the circle. If ∠BOD = 160°, find the values of x and y.

In the given figure, ABCD is a cyclic quadrilateral. If ∠BCD = 100° and ∠ABD = 70°, find ∠ADB.

If ABCD is a cyclic quadrilateral in which AD || BC (In the given figure). Prove that ∠B = ∠C.