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Online Triangle Calculator

Enter any valid input (3 side lengths, 2 sides and an angle or 2 angle and a 1 side) and our calculator will do the rest. (More info on how the tool works)

Loading The Triangle Calculator


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Your 3 side lengths ( ) are invalid .

Side Lengths of do not adhere to the triangle inequality theorem. which states that the sum of the side lengths of any 2 sides of a triangle must exceed the length of the third side. Read more about this rule here.
Test Case (
Case Meaning
1 3,4,5 ,right
2 right triangle
3 tri inequality theorem
4 1 valid obtuse triangle
5 1 valid actue triangle
6 1 valid obtuse triangle
7 1 valid acute
8 Right triangle angle error
9 2 distinct triangles
10 inequality
11 2 distinct triangles
12 2 angles given only (3rd already known, what to do?)
13 1 valid acute
14 no valid triangles
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Status: Calculator waiting for input wating for input

Triangle 1

This is the acute triangle in Quandrant I, for more information on this topic, check out the law of sines ambiguous case
Sides Angles
Side A $$ \angle $$ A
Side B $$ \angle $$ B
Side C $$ \angle $$ C

Triangle 2

This is the obtuse triangle in Quandrant II, for more information on this topic, check out the law of sines ambiguous case
Sides Angles
Side A $$ \angle $$ A
Side B $$ \angle $$ B
Side C $$ \angle $$ C
Auto Calculate
Round to

Why is the calculator saying there's an error when there shouldn't be?
The most frequent reason for this is because you are rounding the sides and angles which can, at times , lead to results that seem inaccurate. In these cases , in actuality , the calculator is really producing correct results. However, it is then rounding them for you- which leads to seemingly inaccurate results and possible error warnings . To see if that is your problem, set the rounding to maximum accuracy.


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Further Reading