In triangles ABC and PQR, AB/RQ = BC/QP = CA/PR, with angle A=80A = 80 degrees and angle B=60B = 60 degrees. Find angle P.

Answer: ∠P=40∘\angle P = 40^\circ

Step-by-step solution

Step 1: Identify Similar Triangles

Given the ratios of corresponding sides ABRQ=BCQP=CAPR\frac{AB}{RQ} = \frac{BC}{QP} = \frac{CA}{PR}, we can conclude that triangle ABC is similar to triangle RQP by the SSS (Side-Side-Side) similarity criterion. It's crucial to match the vertices correctly based on the given side ratios.

Step 2: Determine Corresponding Angles

Since the triangles △ABC\triangle ABC and △RQP\triangle RQP are similar, their corresponding angles must be equal. By matching the vertices from the similarity statement, we find that ∠A\angle A corresponds to ∠R\angle R, ∠B\angle B corresponds to ∠Q\angle Q, and ∠C\angle C corresponds to ∠P\angle P.

Step 3: Calculate Angle C in Triangle ABC

The sum of angles in any triangle is 180∘180^\circ. We are given ∠A=80∘\angle A = 80^\circ and ∠B=60∘\angle B = 60^\circ. We can use this property to find the measure of ∠C\angle C in triangle ABC.

Step 4: Find Angle P

From the similarity of △ABC\triangle ABC and △RQP\triangle RQP, we established that ∠C\angle C corresponds to ∠P\angle P. Therefore, ∠P\angle P must be equal to ∠C\angle C, which we calculated to be 40∘40^\circ.

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