Problem: In triangle ABC,AC=CD and ∠CAB−∠ABC=30∘. Then ∠BAD is:
Answer Choices:
A. 30∘
B. 20∘
C. 2221​∘
D. 10∘
E. 15∘
Solution:
∠BAD=∠CAB−∠CAD=∠CAB−∠CDA
=∠CAB−(∠BAD+∠B).
∴2∠BAD=∠CAB−∠B=30∘;∴∠BAD=15∘.