Q31 / 90 · JEE Main 2021 (26 Aug Shift 2) · Mathematics

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 :

Figure

  • Correct answer
    A
    tan-134
  • B
    tan-112
  • C
    tan-143
  • D
    tan-11

Solution

FigureFrom figure,

sinβ=15tanβ=12
tan(α+β)=2tanα+β=tanα+121-tanα .12=2
α=tan-134

Hence, the correct answer is option: 'A'.

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