Question 136

In a triangle $$ABC, \angle A = \angle B = \angle C$$. The bisectors of the angles $$\angle B$$ and $$\angle C$$ interect at D. Then $$\angle BDC =$$

Solution

In a $$\ \triangle\ $$ ABC,

$$\ \angle\ $$A+$$\ \angle\ $$B+$$\ \angle\ $$C=180$$\ ^{\circ\ }$$

$$\angle\ $$A=$$\angle\ $$B=$$\angle\ $$C=60$$^{\circ\ }$$

since, bisector of $$\angle\ $$B and$$\angle\ $$C meet at D

$$\therefore\ $$  $$\angle\ $$DBC=$$\angle\ $$DCB=30$$^{\circ\ }$$

In$$\triangle\ $$DBC,

$$\angle\ $$DBC+$$\angle\ $$DCB+$$\angle\ $$BDC=180$$^{\circ\ }$$

30$$^{\circ\ }$$+30$$^{\circ\ }$$+$$^{ }\angle\ $$BDC=180$$^{\circ\ }$$

$$\angle\ $$BDC=120$$^{\circ\ }$$


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