# math fromula

thought this would be an appropriate place to share some of what i thought was interesting information to do with the area of a triangle and how numbers co-relate.

To round off a square to 100cm square, one quarter of that area is 25cm square, (10cmx10cm =100/(div)25%=25cm), the area of a right angle triangle with sides measuring ~7.0710cm, equals ~25% of 100cm square, 25cm square of area, (7.0710/2=3.5355 x7.0710=24.9995205).

7.5937 if it is an equilateral triangle.

it is a standard size i use, a handy measurement if you use templates for construction because it in some way represents a metric increment,

thanks,

Kim

(the formula i used is half the base times the height, unless im mistaken i recall that is the correct formula? though i am not a full time mathamatician. for the equalateral triangle i used a web based polygon area calculator.)

## Comments

8 years ago

There was a Greek Guy called Pythagoras who figured-out triangles about 2500 years ago.

L

Reply 8 years ago

And IIRC, someone did so even earlier....although few records of it exist.

Reply 8 years ago

Egyptian engineers certainly used the "3-4-5" relationship to make carpenter's squares. The Babylonians also knew (the "Plimpton 322" tablet) of the general relationship.

Reply 8 years ago

i saw a doco on egyptian building they showed a variation of a water level,

The device is calibrated by the base point(s) located on the surface of water and the position of the string is marked, (probably with a scribe back in the day). perhaps a stonemasons level.

Reply 8 years ago

I thought I remembered something along those lines from high school courses many decades ago (about 4 actually) ;-)

8 years ago

All you've done is to cut your square along the diagonals. Each of the resulting quarters is obviously a right triangle, with hypotenuse equal to the side of the square, and sides both equal to 1/sqrt(2) times the hypotenuse.

It's a pity you just copied the output of some Web-based calculator, rather than learning the underlying geometrical relationships involved.

Reply 8 years ago

It's a pity you just copied the output of some Web-based calculator, rather than learning the underlying geometrical relationships involved.You're so spiteful sometimes... that made me laugh, I'm still smiling.

L

8 years ago

AKA the 1:1:root(2) triangle.