how can you tell wether the triangle with given side lenghts is acute, right, or obtuse?

Question

nothing too complicated; it's a 7th graders homework.

Answer 1

Let the triangle's sides be a, b, and c, in which a and b are both less than c.

If a^2 + b^2 < c^2, then the triangle is obtuse.
If a^2 + b^2 = c^2, then the triangle is right.
If a^2 + b^2 > c^2, then the triangle is acute.

I'm pretty sure about this since I read it in a textbook.

Answer 2

in case you understand the facet lengths then you quite can use Pythagorean thought: C^2=A^2+B^2. Make the longest facet C and then plug interior the numbers and if C^2 is comparable to A^2+B^2 then the triangle is a spectacular triangle. If C^2 is below A^2+B^2 then that is an acute triangle. If C^2 is extra advantageous than A^2+B^2 then that is an obtuse triangle.

Answer 3

Previous answer is incorrect. If all sides are equal, it will be an equilateral triangle and all angles will be acute.

If two sides are equal and the third is different, it will be an iscoceles triangle, but that doesn't say anything about it's angle.

A right angle triangle will be able to use Pythagorean theorem (a^2 + b^2 = c^2).

Sorry, can't come up with more than that.


I'm guessing there is some small remark somewhere in the textbook or it was something the teacher said in class.

Answer 4

acute is an angle LESS then 90 degrees
right is an angle EQUAL to 90 degrees
obtuse is an angle GREATER then 90 degrees

What' i'd do is imagine was a right angle look like in my head (you should know this - imagine an L)
now think, is the angle in the triangle wider then the L or skinnier
wider = obtuse
skinnier = acute

hope that helps a bit

Answer 5

by the angle measurement between the sides. If 180 degrees is a flat line __________________, and 90 degrees is perpedicular lines like the letter L, then anything less than 90 degrees is acute, and anything more than 90 is obtuse. A 90 degree angle is a right angle.

Good question!

Answer 6

if the square of one side equals the sum of squares of other sides then the triangle is right (Pythagoras)
for other two types you can't know unless you have a way to find the angles, or unless you are allowed to draw them - and this is how they look:
http://en.wikipedia.org/wiki/World_War_II

* for the 7th grade remark, I have no clue what Americans study in 7th grade - I knew law of cosines in 7th grade so I would use it to find out angles, but I guess that there must be an easier way to get it

Answer 7

If all side lengths are equal it is a right triangle. If one length is a lot shorter than the other 2 it is acute. If one side is a lot longer than the other two it is considered obtuse.

Answer 8

if the angle is less than 90 degrees it's acute, if it's 90 degrees it a right angle, if it's greater than 90 degrees it's obtuse.

Answer 9

Wow, I guess people don't read entire questions, she said it was for a 7th grader's homework! Anyhow check out:
www.purplemath.com
there is great info there!