Answer:
Option B is correct.i.e.,
Step-by-step explanation:
Given: Pyramid with equilateral triangle as base
Length of side of equilateral triangle = s unit
to find: height of equilateral triangle
Here we use a property of equilateral triangle.
Perpendicular from a vertex on a side and median of that side of a triangle is same in equilateral triangle.
All heights are of equal length. So, we just need to find one height or length of 1 altitude.
Figure of base triangle is attached
In Δ ABC
AB = BC = AC = s unit
AD is height
BD = [tex]\frac{BC}{2}\:=\:\frac{s}{2}\:units[/tex]
Now, In Δ ABD
using pythagoras theorem
BD² + AD² = AB²
[tex](\frac{s}{2})^2+AD^2=s^2[/tex]
[tex]\frac{s^2}{4}+AD^2=s^2[/tex]
[tex]AD^2=s^2-\frac{s^2}{4}[/tex]
[tex]AD^2=\frac{4s^2-s^2}{4}[/tex]
[tex]AD^2=\frac{3s^2}{4}[/tex]
[tex]AD=\sqrt{\frac{3s^2}{4}}[/tex]
[tex]AD=\frac{\sqrt{3}s}{2}[/tex]
[tex]AD=\frac{s}{2}\sqrt{3}[/tex]
Therefore, Option B is correct.i.e., [tex]\frac{s}{2}\sqrt{3}[/tex]