Maths · Trigonometrical identities and trigonometrical functions

and Then is equal to

\( \ln \Delta A B C, B C=A B \) and \( \angle B=80^{\circ} \) Then \( \angle A \) is equal to

  • A. \( 80^{\circ} \)
  • B. \( 40^{\circ} \)
  • C. 50^{\circ} \)
  • D. \( 100^{\circ} \)

Step-by-step solution

In triangle ABC, BC = AB, so angles opposite these sides are equal: ∠A = ∠C. Given ∠B = 80°. Sum of angles is 180°, so ∠A + ∠C = 100°. Since ∠A = ∠C, each is 50°.
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