Triangle calculator

Please enter what you know about the triangle:
Symbols definition of ABC triangle

The calculator solves the triangle specified by three of its properties. Each triangle has six main characteristics: three sides a, b, c, and three angles (α, β, γ). The classic trigonometry problem is to specify three of these six characteristics and find the other three. Of course, our calculator solves triangles from any combinations of main and derived properties such as area, perimeter, heights, medians, etc. Usually by the length of three sides (SSS) or side-angle-side or angle-side-angle.

How does this triangle calculator solve a triangle?

The calculation of the general triangle has two phases:
  1. expert phase - which is different for different tasks. From the entered data, the calculator tries to calculate the sizes of three sides of the triangle. He gradually applies the knowledge base to the entered data, which is represented in particular by the relationships between individual parameters of the triangle. These are successively applied and combined, and the parameters of the triangle calculate. Calculator iterate until the triangle has calculated all three sides.
    For example, from the given area of the triangle and the corresponding side, the appropriate height is calculated. From the known height and angle, the adjacent side, etc., can be calculated. They use knowledge, e.g., formulas (relations) Pythagorean theorem, Sine theorem, Cosine theorem, Heron's formula, solving equations and systems of equations.
  2. The second stage is the calculation of the properties of the triangle from the known lengths of its three sides.

Examples of how to enter a triangle:


a=3 b=4 c=5 ... triangle calc by three sides a,b,c.
B=45 c=10 a=9 ... triangle calc by two sides a,c and included angle B.
A=25 C=80 b=22
A=35 C=26 a=10
a=3 C=90 c=5 ... how to enter right-angled triangle.
a=3 β=25 γ=45 ... triangle calc if we know the side and two angles.
a=3 β=25 T=12 ... triangle calc, if know side, angle, and area of a triangle.
T=2.5 c=2 b=4 ... find side a if know sides b, c, and area of triangle T.
ma=1 b=2.5 c=2 ... calculation of the triangle if we know one median and any two sides.
ma=1 mb=2.5 mc=2 ... triangle calc by three medians.
ha=220, hb=165 hc=132 ... triangle calc by three heights.
a=7 β=40 mc=5 ... triangle calc by one side, one angle, and one median.
a:b:c=2:3:4 T=2.5 ... a triangle where the known side ratio, and its area.
A:B:C=1:4:5 a=2 ... calculating triangle if we know the ratio of the internal angles and one side.
What do the symbols mean?

a, b, c ... sides BC, AC, AB
A, B, C or α, β, γ  ... internal angles
ha, hb, hc ... heights
ma, mb, mc ... medians
T ... area
p ... perimeter
s ... semiperimeter

Triangles in word problems:

  • Center traverse
    trianles Does the middle traverse indeed bisect the triangle?
  • Triangle P2
    1right_triangle Can a triangle have two right angles?
  • Angles
    triangle_1111_1 In the triangle ABC, the ratio of angles is: a:b = 4: 5. The angle c is 36°. How big are the angles a, b?
  • Circles
    three-circles Three circles of radius 95 cm 78 cm and 64 cm is mutually tangent. What is the perimeter of the triangle whose vertices are centers of the circles?
  • Diagonal
    rhombus Can a rhombus have the same length diagonal and side?
  • Height of right RT
    euclid_theorem The right triangle ABC has a hypotenuse c 9 cm long and a part of the hypotenuse cb = 3 cm. How long is the height of this right triangle?
  • Sides of triangle
    rr_triangle2 Triangle circumference with two identical sides is 117cm. The third side measures 44cm. How many cms do you measure one of the same sides?
  • Find the
    triangle1 Find the third interior angle of the triangle ABC where: α = 48°, γ = 65°.
  • Similarity coefficient
    trig12 The triangles ABC and A "B" C "are similar to the similarity coefficient 2. The sizes of the angles of the triangle ABC are α = 35° and β = 48°. Find the magnitudes of all angles of triangle A "B" C ".
  • The sides 3
    equilateral_triangle The sides of an equilateral triangle are 9.4 cm, correct to the nearest one decimal place. Work out the upper bound of the side of this triangle.
  • The triangles
    triangle_rt_taznice The triangles ABC and A'B'C 'are similar with a similarity coefficient of 2. The angles of the triangle ABC are alpha = 35°, beta = 48°. Determine the magnitudes of all angles of triangle A'B'C '.
  • Diagonal
    diamond Can be a diagonal of diamond twice longer than it side?
  • Construction
    taznice7 Construction the triangle ABC, if you know: the size of the side AC is 6 cm, the size of the angle ACB is 60° and the distance of the center of gravity T from the vertex A is 4 cm. (Sketch, analysis, notation of construction, construction)
  • Midpoints
    sierpinski_1 Triangle whose sides are midpoints of sides of triangle ABC has a perimeter 45. How long is perimeter of triangle ABC?
  • Centre of mass
    centre_g_triangle The vertices of triangle ABC are from the line p distances 3 cm, 4 cm and 8 cm. Calculate distance from the center of gravity of the triangle to line p.


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See more information about triangles or more details on solving triangles.