From figure,
sinβ=51tanβ=21
tan(α+β)=2tan(α+β)=1−tanα.21tanα+21=2
α=tan−1(43)
JEE Main 2021 — Mathematics Trigonometry
A 10 inches long pencil AB with mid point C and a small eraser P are placed on the horizontal top of a table such that PC=5 inches and ∠PCB=tan−1(2). The acute angle through which the pencil must be rotated about C so that the perpendicular distance between eraser and pencil becomes exactly 1 inch is :

Held on 26 Aug 2021 · Verified 6 Jul 2026.
tan−1(43)
tan−1(21)
tan−1(34)
tan−1(1)
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