Question

We just had a question about how to derive the formula for the area of a triangle. I've always liked the "visual proof" shown in the first figure. My question is: how to modify that proof to show that it works for an obtuse triangle? (without rotating it).

Answer 1

sorry dotted lines should show correct area in #2

Answer 2

Dumb question. I see now, just slice it into parts.

Answer 3

see in every case you have to draw perpendicular inside a triangle so as to derive the expression ...for example in the last case the obtuse one just bisect the obtuse angle and you'll get the area of triangle for half triangle and multiply it by 2...else you can use measurement...and can calculate it through set squares...i have done this before

Answer 4

I want a visual to proof to show that 1/2 base x height works for this base and height.

Answer 5

area of bigger triangle - area of smaller triangle = 1/2 h bigger base - 1/2 h smaller base

Answer 6

@telltoamit Thanks, I see now.

Answer 7

You're welcome :)