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About Triangles
Area, perimeter and angles from three side lengths.
Units decide the answer as much as the formula does: a room measured in feet gives an area in square feet, and the same room measured in inches gives a figure 144 times larger. Board feet, cubic yards and acres all remain in daily American use.
Geometry questions usually come down to a few relations — the Pythagorean theorem for right triangles, πr² for a circle, length × width × height for a volume — and to whether the measurement is a length, an area or a capacity, since those scale differently. Doubling a shape's dimensions quadruples its area and multiplies its volume by eight.
A triangle is fixed by three of its six parts provided at least one is a side, which is what makes the sine and cosine rules work. The angles must sum to 180 degrees, and one configuration admits two valid triangles from the same figures.
Values are carried at full precision and rounded only for display, and answers arrive in the square or cubic unit that follows from the inputs.
Precision in measurement limits precision in the answer, so a room measured to the nearest inch cannot support an area quoted to four decimals. Lengths, areas and volumes also carry different units, and mixing them is the commonest arithmetic error in building work.
Triangle Calculator sits with the rest of the library's maths work, and it rests on the same geometric arithmetic the way a textbook or an exam paper does. Its answer is only as good as the assumptions standing behind it.
The quantities it works from — side a, side b and side c — are the ones a real geometric question actually turns on, and each carries a convention of its own, set out below.
Mathematics is the one subject here that depends on nothing local: the same theorem holds in Ohio and Osaka, and the same fraction carries the same value everywhere. What changes is how results are written — American schooling teaches decimal notation and long division, and business arithmetic runs on fractions of a dollar.
Precision and rounding are where most practical errors creep in.