Mathematics Stack Exchange
Mathematics Stack Exchange

Questions tagged [triangles]

For questions about properties and applications of triangles.

A triangle is a polygon with three sides. It is an important geometric figure, because any polygon can be subdivided into triangles.

Triangles can be classified by the number of sides they have that have equal length

  • All three sides of an equilateral triangle have equal length.
  • An isosceles triangle has at least two sides of equal length.
  • A scalene triangle is a triangle that is not isosceles, that is, it has no sides with equal length.

A triangle may also be classified by describing its angles. A triangle is said to be a right triangle if it contains a right angle, and obtuse triangle if it contains an obtuse angle, or an acute triangle if all three of its angles are acute.

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Find $A$ or $B$ only given the hypotenuse and $A$ to $B$ ratio of a right triangle?

I'm looking for a formula (or set of formulas) that would be able to determine the $A$, or $B$ value given a right triangle when only $C$ and the ratio $A:B$ is known. I want this mostly for personal use with PC monitors and other boxy shape…
user2620255
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Minimum number of moves required to invert a triangular array of coins?

I cannot find an equation that works WITHOUT rounding. The idea is to find the minimum number of moves to invert a triangle that is made out of counters. The triangle is arranged so that the first row has 1 counter, second row has 2 counters, third…
Liam
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How many ways are there to break up the regular 9-gon into triangles by diagonals?

How many ways are there to break up the regular 9-gon into triangles by diagonals? UPD Guaranteed to be convex - yes. Intersecting "diagonals" be allowed - yes. 2nd UPD It is task for programming course, so there is no need deep math. It is more…
sashaaero
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Trigonometry confusion with triangle in weird question

I was wondering how do you get x from the triangle below:
Code
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Heron's formula to solve a triangle; any faster method?

A triangle has an area of $200cm^{2}$. Two sides of this triangle measure 26 and 40 cm respectively. Find the exact value of the third side. I used Heron's formula to solve this equation, but it involves a long calculation and then the quadratic…
numbermaniac
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Proof of a set of triangles and unit squares

Suppose that there is $S$, a finite set of unit squares. So, $S$ is chosen from a larger grid of unit squares. The unit squares of $S$ are tiled with isoceles right triangles. Each of these triangles has a hypotenuse of $2$. There are $3$ conditions…
mathwhizz
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North has 0 degree and right angle has 90 degree although both are in same position

Before reading trigonometry I guessed that if a line is pointing to north then it has 0 degrees and increases clockwise. But now I see right angle has 90 degree though that is in the same position as north? Is it because angles for navigation are…
user324879
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How can I find Triangle base length?

How can I find base length of the triangle in attached picture? Can I use mid-segment theorem to find the base? Thanks in advance
Mark
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Will two triangles with two equal sides and equal area have same altitude

Consider two triangles ABC and DEF.AB=DE and AC=DF .Also area of triangle ABC is equal to the area of triangle DEF.If we draw an altitude (to one of the equal sides) in both triangles, is it(altitude) necessary to be equal in length.If not then…
user3819404
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Right Triangles

Right triangle ABC has hypotenuse AC, angle CAB=30°, and BC=√2. Right triangle ACD has hypotenuse AD and angle DAC=45°. The interiors of ABC and ACD do not overlap. Find the length of the perpendicular from D onto AB. Can someone please provide a…
Lulu Uy
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Triangle Segments

In a triangle $ABC$, $AB=5$, $BC=16$, $AC= \sqrt{153}$, and $D$ is on segment $BC$. Compute the sum of all possible integral measures of $AD$. I've been having trouble trying to solve this problem and any help would be greatly appreciated. If you…
Lulu Uy
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A strange contradictive problem

First a part of the set of same balls was arranged into an equilateral triangle, 19 balls were not used, but when the sides of this triangle were needed to be one-uped, it was a 5 ball insufficiency. How many balls were in the set? I feel like it's…
MelanieJohansson
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Is it possible that two triangles satisfy these conditions?

Are there two triangles with equal angles and a pair of equal sides which are not congruent? If yes, please give an example.
chen h.
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Geometry: Measure of angles

The area of a triangle is equal to 48 cm^2 and two if its sides measure 12 cm and 9 cm, respectively. Find the possible measures of the included angles of the given sides.
Ell
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The vertices of a triangle are A(-1, 1) B(4,0) and C(1,6) Find the equation of the altitude of the triangle ABC drawn from A.

I need some help understanding the process of how you go about answering this question: The vertices of a triangle are A(-1, 1) B(4,0) and C(1,6) Find the equation of the altitude of the triangle ABC drawn from A. Not going to lie, in a higher maths…
Johnny Mccrum
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