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Right triangle, hypotenuse 13, find the median to it

Step by step, with the reason for every step · Medians and the centroid · Geometry

Step by step

The question

Question: in a right triangle the hypotenuse B C is 13: find the median A M to the hypotenuse.

1 Use the semicircle rule

The right angle is at A.

The median A M goes to M, the middle of the hypotenuse B C.

Draw the circle with B C as its diameter.

The angle in a semicircle is 90°, so A is on this circle too.

M is the center.

M A, M B and M C are all radii: all the same length.

2 Half the hypotenuse

The radius is half the diameter: 13 divided by 2 is 6.5.

AM = 13 ÷ 2 = 6.5

Careful!

This works for the median to the hypotenuse of a right triangle.

Not for any median.

Careful: only to the hypotenuse, in a right triangle

3 Check

Let's check: M B and M C are 6.5 each, and together they make B C, 13.

So it is right!

MB = MC = 6.5, MA = 6.5: MB + MC = 13 = BC

Let's look back.

First: use the semicircle rule.

Then: half the hypotenuse.

Last: check.

Answer
Careful: only to the hypotenuse, in a right triangle

Your turn

Try this one yourself, then check:

Find AM.
Show the answer
AM = 8

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