Triangle SAS area calculator
Find area from two triangle sides or two convex-quadrilateral diagonals and the angle between them.
Formula
A = ab sin(θ)/2; a, b are two triangle sides or two convex-quadrilateral diagonals.
Side / diagonal a: 6 cm · Side / diagonal b: 4 cm · Angle between lengths θ: 90 ° · Area ≈ (6 cm × 0.01 m/cm)×(4 cm × 0.01 m/cm)×sin((90 ° × 0.01745329252 rad/°))÷2×10000
How to use
- Enter two triangle sides or both quadrilateral diagonals.
- Enter the angle between the chosen lengths.
- Read the area in cm².
Examples
- Sides 4 and 5 cm with included angle 150° give area 5 cm².
- A convex quadrilateral with diagonals 8 and 5 cm crossing at 30° has area 10 cm².
Frequently asked questions
Which angle do I need?
For a triangle, use the included angle at the shared vertex. For a quadrilateral, use the angle where the diagonals cross.
Can I enter an obtuse angle?
Yes. Use 0° < θ < 180°; very near endpoints are excluded. Supplementary angles have the same sine.
Which quadrilaterals are supported?
Planar convex quadrilaterals. Enter their two diagonals, not two side lengths; crossed figures are excluded.
Sources
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