Triangle Calculator
Calculate area, perimeter and angles of a triangle. With side lengths or angles. Online calculator with solution path and worked examples.
Enter at least three values (e.g. three sides or two sides and one angle).
Result
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Note: These calculations are for informational purposes only and do not replace professional tax or financial advice. All information without guarantee.
Frequently Asked Questions
How do I calculate the area of a triangle?
Area equals base times height divided by 2. Alternatively, use Heron's formula with three sides: Area equals the square root of s(s-a)(s-b)(s-c), where s is the semi-perimeter.
What is the Pythagorean theorem?
In a right triangle, the square of the hypotenuse equals the sum of the squares of the other two sides: a squared plus b squared equals c squared. Only valid for right triangles.
What is the Triangle Calculator?
The triangle calculator computes sides, angles, area, perimeter and heights of a triangle from the given values.
How does the Triangle Calculator work?
Enter at least three values (e.g. 3 sides or 2 sides + 1 angle). The calculator computes all missing values using the sine rule, cosine rule and area formulas. For right triangles the Pythagorean theorem is applied.
Key Data and Facts
Area formula: A = 0.5 * base * height. Pythagoras: a squared + b squared = c squared. Sum of interior angles: always 180 degrees. Cosine rule: c squared = a squared + b squared - 2ab * cos(C).
Step-by-Step Guide
How to calculate ein Dreieck step by step: 1. Bekannte Groessen enter: Mindestens 3 Werte (Seiten und/oder Winkel) sind noetig. Moegliche Kombinationen: SSS (3 Seiten), SWS (2 Seiten + eingeschlossener Winkel), WSW (2 Winkel + eingeschlossene Seite), SSW (2 Seiten + gegenueberliegender Winkel). 2. Fehlende Seiten calculate: Kosinussatz: c2 = a2 + b2 - 2ab x cos(C). Sinussatz: a/sin(A) = b/sin(B) = c/sin(C). 3. Fehlende Winkel: Winkelsumme = 180 Grad. Einzelner Winkel: cos(C) = (a2 + b2 - c2) / (2ab). 4. Flaeche calculate: A = 0,5 x Grundseite x Hoehe. Oder Heronsche Formel: A = Wurzel(s(s-a)(s-b)(s-c)) mit s = (a+b+c)/2. 5. Umfang: U = a + b + c. 6. Hoehen, Seitenhalbierende und Inkreisradius werden ebenfalls angezeigt. Fuer rechtwinklige Dreiecke gilt der Satz des Pythagoras: a2 + b2 = c2.
Calculation Example
Dreieck mit a = 5 cm, b = 7 cm, C = 60 Grad: c2 = 25 + 49 - 2 x 5 x 7 x cos(60) = 74 - 35 = 39, c ≈ 6,24 cm. Flaeche = 0,5 x 5 x 7 x sin(60) ≈ 15,16 cm2.
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