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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Finding a side of triangle with only 2 angles and 1 side; and how to enter on calculator

I'm really bad at this and don't even know the names of the different things, so here it is as plain as I can ask. I have a trigonometry calculator & need to know how I should enter the formula to get my answer. I have a triangle. One angle is 90…
BlueJade
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a triangle problem of angles

suppose in triangle ABC , angle of BAC is 60 degree. if K is intersection point of [CM] median(for segment[AB] )and [BN] altitude. also suppose |KM|=1 cm and |CK|=6 cm calculate angels of triangle ABC?
agustin
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Let ABC be a triangle such that AB = √2 BC = √3 and ∠ABC = 120°

Let ABC be a triangle such that AB = √2 BC = √3 and ∠ABC = 120°. What is the length of line AC? What is the area of triangle ABC?
Takina
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Find 3rd point of triangle knowing A and B coordinates and all the angles

I got a triangle, knowing A and B coordinates and all the three angles, how can I calculate C coordinates? Schema
Kevin Castejon
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Find 3rd point of triangle with the opposite angle

I got a triangle, I know A and B coordinates, I know all angles, how can I calculate C coordinates? Schema
Kevin Castejon
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Do altitudes produce similar triangles(Method for solving question)?

Question: If triangle PQR has sides 40, 60, and 80, then the shortest altitude is K times the longest altitude. Find the value of K. Original Method: I've tried to do the problem by just draw a altitude, and then use cos90 or tan90 to find the…
DarkRunner
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Calculus of median and bisector

In the triangle ABC we draw the median segment AD and the bisector BE. We know that AB=7, BC=18 ed EA=ED. How is the length of AC?
G. Gadda
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Triangle: One side, opposite angle and ratio of other sides given

I try to program a slope failure simulation in Matlab and now the following problem occurred: Let's say I've got to points $A(X_1,Y_1)$ and $B(X_2,Y_2)$, which build one side $c$ of a triangle. Additionally I've got the opposite angle $\gamma$ of…
Screeper
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Difference between $\angle ABC = 90^o$ and $\angle B = 90^O$

When you have a random triangle $\triangle ABC$, what exactly is the difference between $\angle ABC = 90^o$ and $\angle B = 90^o$? In which cases is it the same, in which cases is it different? What implications does $\angle ABC = 90^o$ have that…
JohnPhteven
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What is the value for angle EGB?

(OBM) In a rectangle ABCD, E is the midpoint of side BC and F is the midpoint of side CD. G is the point that represents the intersection between DE and FB. Angle EAF is 20º. What is the value for the angle EGB? Sorry, I can't photograph my…
Vinicius Guimarães
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How to prove joining mid points of sides parallel to BC we get the median through A?

Consider a triangle ABC. Let D is the mid point of side BC and let EF is a line segment parallel to BC and E , F lie on side AB , AC respectively. How can one prove that if the median AD of triangle cuts the line seqment EF at P then P is mid point…
Matt
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Calculate angles of an isosceles triangle knowing only the length of the base

Is there a way to find the angles of an isosceles triangle if you only know the length of the base? Here's an image: isosceles triangle If I know the length in red, is it possible to figure out what the angles in purple are? Probably not, so in that…
Mortlanka
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Pythagorean triangle sides

Can all numbers $a, b, c$ that $a^2+b^2=c^2$ be sides of a right triangle? ($c$ is the hypotenuse) I saw this problem: Find the number of right triangles that the hypotenuse and one side are both prime numbers. I said that we don't have any…
user325789
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Moving 1 by 1 on a hypotenuse

I have a right triangle. The h represents a projectile that I want to move at a specific speed. No matter the dimensions the right triangle, I want to move the same speed on its h. I guess I am asking, how do I figure out the change in the x and y…
Evan Carslake
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How can I be sure it's always possible to draw perpendicular lines (altitudes) inside triangles?

So, I've come across this proof for the ratio of corresponding sides of similar triangles on the internet, but the proof requires that we draw a perpendicular line (an altitude) inside the triangle. It might seem a silly question, but how can I be…
daniels
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