A four-sided figure
For a quadrilateral inscribed in a circle, his area rule extends the form of Heron’s triangle formula.
16 / ANTIQUITY TO THE RENAISSANCE
Brahmagupta
A coin you own and a debt you owe cancel out. Brahmagupta turned that everyday idea into rules for calculating with negative numbers and zero.
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01 / SIGNED NUMBERS
What is left after the debts are paid?
Coins are fortunes (+1) and debt slips are debts (−1). A coin paired with a slip is worth zero.
Zero pairs never change the worth. That lets you take away a debt you don’t have, and see that taking away a debt adds one.
Take away:
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THE IDEAA fortune and an equal debt make zero. Taking away a debt raises the worth: subtracting a negative is adding, so 2 − (−3) = 5.
The person behind the ideas
- Wrote the Brahmasphutasiddhanta in 628.
- Described positive and negative quantities as fortunes and debts.
- Also developed methods in algebra, geometry and astronomy.
More of the mathematics
Astronomical calculation
His writings connect numerical procedures with calculations of celestial motion.