Online calculator and formulas for calculating an isosceles triangle
This function calculates various parameters of an isosceles triangle. Select the two elements that you know and enter the appropriate values. Then click on Calculate.
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An isosceles triangle has at least two sides of equal length.
The angles opposite the sides of the same length are consequently of the same size.
Two values are required for a complete calculation, at least one side of them.
Base \(\displaystyle a\)\(\displaystyle a=2 · b ·cos(α)\)
Side \(\displaystyle b\)\(\displaystyle b=\frac{a}{2 · cos(α)}\)\(\displaystyle b=\frac{h}{sin(α)}\)
Height \(\displaystyle h\)\(\displaystyle h=b · sin(α)\)\(\displaystyle h=\frac{a}{2} · tan(α)\)\(\displaystyle h=\sqrt{b^2 - \frac{a^2}{4}}\)
Perimeter\(\displaystyle P\)\(\displaystyle P=a+2 · b\)
Area \(A\)
\(\displaystyle A=\frac{a·h}{2}\)\(\displaystyle A=\frac{b^2·sin(2·α)}{2}\)
Angle \(\displaystyle α\)\(\displaystyle α=atan\left(\frac{2 · h}{a}\right)\)
Angle \(\displaystyle γ\)\(\displaystyle γ= 180 -2 · α\)
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