Shortcut Trick
According to geometric properties, the lengths of the medians of a triangle are directly related to the lengths of its sides.
If all three medians of a triangle are equal in length, then all three sides of the triangle must also be equal.
A triangle with all three equal sides is defined as an equilateral triangle.
∴ The correct answer is equilateral triangle.
Alternate Method
A
B
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F
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AD = BE = CF
Given:
Let ABC be a triangle with side lengths a, b, and c corresponding to sides BC, AC, and AB.
Let ma, mb, and mc be the medians drawn to sides a, b, and c respectively.
It is given that all medians are equal: ma = mb = mc.
Formula Used:
By Apollonius's theorem, the length of a median ma is calculated as:
ma = ½√(2b2 + 2c2 − a2)
Calculation:
⇒ ma2 = ¼(2b2 + 2c2 − a2)
⇒ Similarly, mb2 = ¼(2a2 + 2c2 − b2)
⇒ Since the medians are equal, ma2 = mb2
⇒ ¼(2b2 + 2c2 − a2) = ¼(2a2 + 2c2 − b2)
⇒ 2b2 + 2c2 − a2 = 2a2 + 2c2 − b2
⇒ 2b2 − a2 = 2a2 − b2
⇒ 3b2 = 3a2
⇒ a2 = b2
⇒ a = b (as side lengths cannot be negative)
⇒ Following the exact same process for mb = mc, we get b = c.
⇒ Thus, a = b = c.
⇒ Since all three sides are equal, the triangle must be an equilateral triangle.
∴ The correct answer is equilateral triangle.
Additional Information
Isosceles Triangle Medians
If exactly two medians of a triangle are equal in length, the corresponding two sides are also equal, making it an isosceles triangle.
Centroid Property
The point of intersection of all three medians is called the centroid. It uniquely divides each median in a 2:1 ratio, with the larger segment originating from the vertex.
Apollonius's Theorem
This theorem establishes a crucial relationship between sides and medians: b2 + c2 = 2(ma2 + (a/2)2).