Question : ABC is an equilateral triangle points D, E and F are taken in sides AB, BC and CA respectively so that, AD = BE = CF. Then DE, EF, and FD enclose a triangle which is:
Option 1: equilateral
Option 2: isosceles
Option 3: right angled
Option 4: none
Correct Answer: equilateral
Solution : Given: ABC is an equilateral triangle points D, E and F are taken in sides AB, BC and CA respectively so that, AD = BE = CF. Now, AB = BC = CA and AD = BE = CF So, AD = BD = BE = EC = CF = AF ⇒D, E, and F are midpoints of the sides AB, BC and AC, respectively. Thus, DF || BC and DF = $\frac{1}{2}$BC Similarly DE = $\frac{1}{2}$AC and EF = $\frac{1}{2}$AB So, DE = EF = DF $\therefore \triangle$DEF is an equilateral triangle. Hence, the correct answer is equilateral.
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Question : $\triangle$ABC is an equilateral triangle in which D, E, and F are the points on sides BC, AC, and AB, respectively, such that AD $\perp$ BC, BE $\perp$ AC and CF $\perp$ AB. Which of the following is true?
Option 1: 4AC$^2$ = 5BE$^2$
Option 2: 3AC$^2$ = 4BE$^2$
Option 3: 2AB$^2$ = 3AD$^2$
Option 4: 7AB$^2$ = 9AD$^2$
Question : In a triangle ABC, AD, BE, and CF are three medians. The perimeter of ABC is:
Option 1: equal to $(\overline {AD}+\overline{BE}+\overline{CF})$
Option 2: greater than $(\overline {AD}+\overline{BE}+\overline{CF})$
Option 3: less than $(\overline {AD}+\overline{BE}+\overline{CF})$
Option 4: none of these
Question : In a $\triangle ABC$, D and E are two points on AB and AC respectively such that DE || BC, DE bisects the $\triangle ABC$ in two equal areas. Then the ratio DB : AB is:
Option 1: $1:\sqrt2$
Option 2: $1:2$
Option 3: $\left ( \sqrt2-1 \right ):\sqrt2$
Option 4: $\sqrt2:1$
Question : The sides AB, BC, and AC of a $\triangle {ABC}$ are 12 cm, 8 cm, and 10 cm respectively. A circle is inscribed in the triangle touching AB, BC, and AC at D, E, and F respectively. The difference between the lengths of AD and CE is:
Option 1: 4 cm
Option 2: 5 cm
Option 3: 3 cm
Option 4: 2 cm
Question : $\triangle \mathrm{ABC}$ and $\triangle \mathrm{DEF}$ are two triangles such that $\triangle \mathrm{ABC} \cong \triangle \mathrm{FDE}$. If AB = 5 cm, $\angle$B = 40° and $\angle$A = 80°, then which of the following options is true?
Option 1: DF = 5 cm, $\angle$E = 60°
Option 2: DE = 5 cm, $\angle$F = 60°
Option 3: DE = 5 cm, $\angle$D = 60°
Option 4: DE = 5 cm, $\angle$E = 60°
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