The base of an equilateral triangle is along the line given by 3 x+4 y=9. If a vertex of the triangle is (1,2), then the length of a side of the…
JEE Main 2014 — Mathematics Coordinate Geometry
2014mcqeasy
The base of an equilateral triangle is along the line given by 3x+4y=9. If a vertex of the triangle is (1,2), then the length of a side of the triangle is:
Official previous-year question
Held on 11 Apr 2014 · Verified 6 Jul 2026.
Options
A
1523
B
1543
C
543
D
523
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Solution
Shortest distance of a point (x1,y1) from line ax+by=c is d=a2+b2ax1+by1−c Now shortest distance of P(1,2) from 3x+4y=9 is PC=d=32+423(1)+4(2)−9=52 Given that △APB is an equilateral triangle Let ' a ' be its side then PB=a,CB=2a Now, In ΔPCB,(PB)2=(PC)2+(CB)2 (By Pythagoras theorem) a2=(52)2+4a2a2−4a4=254⇒43a2=254a2=7516⇒a=7516=534×33=1543
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