Find the third angle of a triangle
The sum of all interior angles in a triangle is always 180 degrees.
Write down the two known angles A and B in degrees.
Why: You need exactly two angles to find the third. Make sure your values are clearly recorded.
Check that both angles are positive and each is less than 180 degrees.
Why: Triangle angles must each be between 0° and 180°. Negative or excessive values indicate measurement errors.
Verify that A + B is less than 180 degrees.
Why: If A + B ≥ 180°, there's no room for angle C. This catches impossible triangles before calculation.
Apply the formula: C = 180 - A - B
Why: This formula derives from the geometric fact that all interior angles in any triangle sum to 180 degrees.
Check that C is positive and that A + B + C = 180 exactly.
Why: This verification confirms the calculation is correct and the triangle is geometrically valid.
Surveying a Triangular Plot
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