Find the missing angle of a right triangle calculator

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• Right Triangle Calculator

Enter two values of a right triangle and select what to find.
The calculator gives you a step-by-step guide on how to find the missing value. Calculator works with decimal numbers, fractions and square roots.

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The missing value is:

Provide any two values of a right triangle
calculator works with decimals, fractions and square roots (to input $ \color{blue}{\sqrt{2}} $ type $\color{blue}{\text{r2}} $)

leg $ a $

=

leg $ b $

=

hyp. $ c $

=

angle $ \alpha $

=

angle $\beta$

=

Area $ A $

=

EXAMPLES

Find the hypotenuse of a right triangle in whose legs are $ a = 18~ cm $ and $ b = \dfrac{13}{2} cm $.

Find the angle $\alpha$ of a right triangle if hypotenuse $ c = 8~cm$ and leg $ a = 4~cm$.

Find the hypotenuse $ ~ c ~$ if $\alpha = 50^{\circ} $ and leg $ a = 8 $.

Find the area of a right triangle in which $\beta = 30^{\circ}$ and $b = \dfrac{5}{4} cm$

TUTORIAL

Right triangle calculations

The calculator uses the following formulas to find the missing values of a right triangle:

Pythagorean Theorem:	$$ a^2 + b^2 = c^2 $$
Area:	$$ A = \frac{a b}{2} $$
Trig. functions:	$$ \sin \alpha = \frac{a}{c} $$
	$$ \cos \alpha = \frac{b}{c} $$
	$$ \tan \alpha = \frac{a}{b} $$

Example 01 :

Find hypotenuse $ c $ of a right triangle if $ a = 4\,cm $ and $ b = 8\,cm $.

Solution:

When we know two sides, we use the Pythagorean theorem to find the third one.

$$ \begin{aligned} c^2 &= a^2 + b^2 \\[ 1 em] c^2 &= 4^2 + 8^2 \\[ 1 em] c^2 &= 16 + 64 \\[ 1 em] c^2 &= 80 \\[ 1 em] c &= \sqrt{80} \\[ 1 em] c &= \sqrt{16 \cdot 5} \\[ 1 em] c &= 4\sqrt{5}\\ \end{aligned} $$

Example 02 :

Find the angle $\alpha$ of a right triangle if hypotenuse $ c = 14~cm$ and leg $ a = 8~cm$.

Solution:

In order to find missing angle we can use the sine function

$$ \begin{aligned} \sin \alpha & = \frac{a}{c} \\[1 em] \sin \alpha & = \frac{8}{14} \\[1 em] \sin \alpha & = 0.5714 \\[1 em] \alpha &= \sin^{-1} (0.5714) \\[1 em] \alpha & \approx \, 39^{o} \end{aligned} $$

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Angle and hypotenuse of right triangle

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[10]  2020/09/11 09:57   50 years old level / Others / Very /

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