An equilateral triangle has side length 6. If a horizontal line is placed in the figure such that the triangle is split in to two sections of equal area, how high must the line be?
Since the height of an equilateral triangle in terms of its side s is s√3/2, the height of the triangle is 6√3/2 = 3√3 and so the area is (1/2)(6)(3√3) = 9√3.
If we draw a horizontal line a height of h from the base of the triangle, the region is split into two regions: the lower region consisting of a trapezoid of height h and the upper region consisting of a triangle of height 3√3 - h.
Since the upper triangle and the triangle itself are similar triangles, the base and height are proportional. If we let x denote the base of the length of the upper triangle, we have:
(S. of small triangle)/(S. of big triangle) = (Ht. of small triangle)/(Ht. of big triangle)
The line will be 5 high. Putting the line down the middle makes a right angled triangle. we know the longest side is 6, therefore using pythagoras, 6^2=a^2 +b^2. We know one of the sides is 3, because the line drawn down the middle divides one of the original triangle's sides in two. So, 6^2=3^2+b^2. When you do the calculation, it is easy to see that b is 5. 36=9 + ?. It is now clear that ? is 25 (Square root of 25 is 5).
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EDIT: Fixed solution below.
Since the height of an equilateral triangle in terms of its side s is s√3/2, the height of the triangle is 6√3/2 = 3√3 and so the area is (1/2)(6)(3√3) = 9√3.
If we draw a horizontal line a height of h from the base of the triangle, the region is split into two regions: the lower region consisting of a trapezoid of height h and the upper region consisting of a triangle of height 3√3 - h.
Since the upper triangle and the triangle itself are similar triangles, the base and height are proportional. If we let x denote the base of the length of the upper triangle, we have:
(S. of small triangle)/(S. of big triangle) = (Ht. of small triangle)/(Ht. of big triangle)
==> x/6 = (3√3 - h)/(3√3)
==> x = (6√3 - 2h)/√3
Thus, the area of the upper triangle is:
A = (1/2)[(6√3 - 2h)/√3](3√3 - h) = [(6√3 - 2h)(3√3 - h)]/(2√3).
(Made a dumb mistake about the height here for some reason)
Since we require that the area of this triangle is to be half of the total area (9√3/2), we need to solve:
[(6√3 - 2h)(3√3 - h)]/(2√3) = 9√3/2
==> (6√3 - 2h)(3√3 - h) = 27
==> 54 - 6h√3 - 6h√3 + 2h^2 = 27
==> 2h^2 - 12h√3 + 27 = 0.
Solving with the Quadratic Formula gives:
h = (6√3 + 3√6)/2 ≈ 8.87 units and h = (6√3 - 3√6)/2 ≈ 1.52 units.
Since h = (6√3 + 3√6)/2 would place the line outside of the triangle, we pick h = (6√3 - 3√6)/2.
Therefore, the line should be (6√3 - 3√6)/2 units from the base.
I hope this helps!
If the equilateral triangle has side length 6, then its height is 3√3 and its area is:
A = (6)²√3/4 = 9√3 sq. units
Let h be the height at which the horizontal line is placed.
The height of the upper section (Triangle) will be: 3√3 - h(not necessary since it's an equilateral triangle which is of length L let's say).
The height of the lower section (Trapezoid) will be : h
Area of the upper section of the triangle which is of length L.
L²√3 = 18√3
L = √18 = 3√2
(h)(6 + L) = 9√3
h = 9√3/[6 + 3√2] = 1.5219
The line will be 5 high. Putting the line down the middle makes a right angled triangle. we know the longest side is 6, therefore using pythagoras, 6^2=a^2 +b^2. We know one of the sides is 3, because the line drawn down the middle divides one of the original triangle's sides in two. So, 6^2=3^2+b^2. When you do the calculation, it is easy to see that b is 5. 36=9 + ?. It is now clear that ? is 25 (Square root of 25 is 5).
Hope this helps.
I can only guess the line you ******.
However using pythag it should be 6^2 - 3^2 then square routed.
Which is the route of 27. Or in surd form 3route3
DON'T GIVE UP THY DAY JOB HAR HAR HAR **snort**