Q28 / 55 · KVPY 2020 (SA) · Mathematics

In a triangle ABC, the altitude AD and the median AE divide ∠A into three equal parts. If BC=28, then the nearest integer to AB+AC is

  • Correct answer
    A
    38
  • B
    37
  • C
    36
  • D
    33

Solution

Figure

ΔABE is isosceles ⇒BD=DE=7

ΔADC:tan90-2θ=AD21    ...1

ΔADE:tan90-θ=AB7    ...2

Divide tanθtan2θ=13⇒1-tan2θ2=13

1-tan2θ=23⇒tanθ=13⇒θ=30°

ΔABD:cos90-θ=BDC=sinθ

C=7cosecθ=14

∆ADC:cos90-2θ=DCb=sin2θ

b=423=143

[b+c]=38

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

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