Side BCof ΔABChs been produced to D on left and to E on right-hand side of BC such that ∠ABD=125∘and ∠ACE=130∘.Then,∠A=?
(a)50∘ (b)55∘ (c)65∘ (d)75∘
ANSWER:
(d) 75∘
We have :
∴ ∠ABD+∠ABC=180°∵DEisastraightline⇒125°+∠ABC=180°⇒∠ABC=55∘
Also,
∠ACE+∠ACB=180°⇒130°+∠ACB=180°⇒∠ACB=50°∴∠BAC+∠ABC+∠ACB=180∘ Sum of the angles of a triangle
⇒ ∠BAC+55°+50°=180°⇒∠BAC=75°⇒∠A=75∘