Any day is a good time to celebrate math, but today's date can actually be written as a mathematical theorem!

Pythagorean Theorem Day occurs any time the date aligns to the Pythagorean Theorem.

This theorem suggests that for any right triangle with with sides of length a, b and c:

a

^{2}+ b^{2}= c^{2}
The date Aug. 15, 2017, when written as 8 - 15 - 17, can be used to form the triangle side lengths 8, 15 and 17.

We can use those lengths to write the Pythagorean Theorem:

8

^{2}+ 15^{2}= 17^{2}
Check this by doing the math to see if the solution is correct: 64 + 225 = 289

Can you figure out when the last Pythagorean Theorem Day was held?

See below for the answer.

Can you guess when the next one will be?

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The last Pythagorean Theorem Day was just last year: 1/15/16

The next one will be in three years: 12/16/20

How are you celebrating Pythagorean Theorem Day? Share your ideas in the comment box.

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Happy 40th Anniversary, Excel Math!