Question

What is the length of line BD in the equilateral triangle ABC shown below?

Answer 1

It says 10, right?
In which case, do you know the 30-60-90 special triangle?


This triangle also half of an equilateral triangle. 2x is the 'diagonal' side of one half of your triangle, so 2x=10.

Do you have it?

Answer 2

x=5

Answer 3

so the answer is 5, right?

Answer 4

the length of line BD

Answer 5

Not quite. The right angle is made from the perpendicular line dashed line in the middle of your equilateral triangle. You need to orient yourself so that the 30-60-90 triangle is the right half of your triangle.
so the length of BD is represented by \[x \sqrt{3}\]

Answer 6

so it's 5√(3)?

Answer 7

yes :) that's it!

Answer 8

thnx!