Just be quick with calculations

Geometry Level 2

A B C ABC is an equilateral triangle such that vertices B , C B,C lie on two parallel lines at a distance of 6 units. If A A lies between the parallel lines at a distance 4 units from one of them, then the length of the side of the triangle is of the form A B C \large{A\sqrt{\frac{B}{C}}} , where A , B , C A,B,C are co prime natural numbers.

Find A + B + C A+B+C .


The answer is 14.

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3 solutions

Tanishq Varshney
May 3, 2015

the missing steps are

as θ \theta is acute taking only positive value

Let vertical side be tilted through α \angle \alpha s i d e x = 6 C o s α a n d x S i n ( 30 α ) = 2. S i n ( 30 α ) = 2 C o s α 6 1 2 C o s α 3 2 S i n α = C o s α 3 3 2 S i n α = C o s α 6 T a n ( α ) = 1 3 3 S e c ( α ) = 28 27 x = 6 S e c ( α ) x = 4 7 3 x = A B C A + B + C = 14 \therefore side~x=\dfrac{6}{Cos\alpha}~~ and~~ x*Sin(30-\alpha)=2. ~\\\implies Sin(30-\alpha)=2*\dfrac{Cos \alpha}{6}\\\dfrac 1 2 *Cos \alpha-\dfrac{\sqrt 3}{2}*Sin \alpha=\dfrac{Cos \alpha}{3}\\ \implies~-\dfrac{\sqrt 3}{2}*Sin \alpha=- \dfrac{Cos \alpha}{6}\\ \implies ~Tan (\alpha)=\dfrac 1 {3\sqrt 3 }\\Sec( \alpha)=\dfrac{\sqrt{28} } {\sqrt {27}}\\x=6*Sec(\alpha)\\x=4*\sqrt{\dfrac 7 3 }\\x=A*\sqrt{\dfrac {B}{ C} }\\A+B+C= \color{#D61F06}{\large14}

Are u really 87 yrs old!!

Kyle Finch - 6 years, 1 month ago

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It is OK to question. But wanted to know why did your question? Just wanted to know. Yes I am running 78.

Niranjan Khanderia - 6 years, 1 month ago
Ahmad Saad
Nov 5, 2015

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