An equilateral triangle has an altitude of 21 inches. What is the side length of the triangle?

14 2

7 2

7 3

14 3

7

Step-by-step explanation:

the altitude creates two congruent 30-60-90° triangles

the ratio of the sides in a 30-60-90°, respectively, are 1 : : 2

therefore we can set up a proportion to find the side length:

let 'x' = side length of equilateral Δ

/ 1 = 21 / x

cross-multiply:

x = 21

x = 21 /

rationalize the denominator by multiplying numerator and denominator by

21 / · = 21 / 3 or 7

for this case we have by definition, if two lines are perpendicular, then the product of their slopes is -1.

then, given the following line:

so,

we are looking for m_ {2}:

then, the line is given by:

we find "b" replacing the given point:

finally, the equation is:

option c