Angles in Triangles

No matter the shape of a triangle — equilateral, isosceles, scalene, right-angled — the sum of its three interior angles is always $180°$.

You can prove this by tearing off the three corners of any paper triangle and placing them together: they always form a straight line ($180°$).

To find a missing angle in a triangle, add the two known angles and subtract from $180°$:

$$\text{missing angle} = 180° - (\text{angle 1} + \text{angle 2})$$

Adjust angles A and B with the buttons. Angle C updates automatically so that the three always sum to $180°$.

Watch it work

Question: A triangle has angles of $52°$ and $76°$. Find the third angle.

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