Suriin ang IDNStudy.com para sa mabilis na mga solusyon sa iyong mga problema. Ang aming komunidad ay handang magbigay ng malalim at praktikal na mga solusyon sa lahat ng iyong mga katanungan.

If the altitude of an equilateral triangle is 2 cm shorter than its side, find the length of its side.

Sagot :

use the illustration i've made as reference. (see attachment)
taking the left right triangle, we can use Pythagorean Theorem
[tex]x^2 = (\frac{x}{2})^2 + (x-2)^2 [/tex]
[tex]x^2 = \frac{x^2}{4} + (x^2 - 4x +4)[/tex]
[tex]x^2 = \frac{x^2}{4} + x^2 - 4x + 4[/tex]
multiply the whole equation with 4
[tex]4x^2 = x^2 + 4x^2 - 16x + 16[/tex]
transpose all the terms from left to right, equating it to zero
[tex]0=4x^2 - 4x^2 + x^2 - 16x + 16 [/tex]
or
[tex]4x^2-4x^2+x^2-16x+16=0[/tex]
[tex]x^2 - 16x + 16 = 0[/tex]
using quadratic formula
[tex]x = \frac{-b (+-) \sqrt{b^2-4ac} }{2a} [/tex]
a = 1
b = -16
c = 16
[tex]x = \frac{-(-16) (+-) \sqrt{(-16)^2-4(1)(16)} }{2(1)} [/tex]
[tex]x = \frac{16 (+-) \sqrt{256-64} }{2} [/tex]
[tex]x = \frac{16(+-) \sqrt{192} }{2}[/tex]
[tex]x = \frac{16(+-) \sqrt{64(3)} }{2}[/tex]
[tex]x = \frac{16(+-) 8\sqrt{3}}{2}[/tex]
[tex]x = 8 (+-) 4 \sqrt{3}[/tex]
[tex]x_1 = 8 + 4 \sqrt{3}[/tex]
or
[tex]x_1 = 14.9282 units[/tex]
[tex]x_2 = 8 - 4\sqrt {3}[/tex]
or
[tex]x_2 = 1.0718 units[/tex]
therefore you can have the value of the side as 14.9282 units and/or 1.0718 units
View image Shinalcantara