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GATE CSE 2020 Q9: Sum of acute angles of two perpendicular lines with the X-axis

Question

Two straight lines are drawn perpendicular to each other in X-Y plane. If α\alpha and β\beta are the acute angles the straight lines make with the X-axis, then α+β\alpha + \beta is _____.

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Answer: B (official GATE 2020 final answer key)

Concept used: The two lines and the X-axis form a triangle with a right angle where the lines meet.

First step: In that triangle the angles at the X-axis are α\alpha and β\beta, and the third angle is 90°.

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Source: official GATE 2020 CS question paper and final answer key, organised by IIT Delhi. Question paper · Answer key

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