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history of mathematics - National STEM Centre

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754<br />

12 Summaries and exercises<br />

5 Arab <strong>mathematics</strong><br />

Chapter summary<br />

• some inheritance problems from Islamic law (Activity 5.1).<br />

• how Arabic work on trigonometry built on the work <strong>of</strong> Ptolemy to compile<br />

trigonometric tables (Activities 5.2 and 5.3)<br />

• examples <strong>of</strong> problems from the East worked on by Arab mathematicians<br />

(Activity 5.4)<br />

• how Thabit ibn Qurra investigated amicable numbers (Activity 5.5)<br />

• some Chinese methods for solving equations which were available to the Arabs<br />

(Activities 5.6 and 5.7)<br />

• the origins <strong>of</strong> the word 'algebra' (text before Activity 5.8)<br />

• the six types <strong>of</strong> quadratic equation solved algorithmically, with geometric<br />

justification, by al-Khwarizmi (text and Activity 5.8)<br />

• some <strong>of</strong> the 19 types <strong>of</strong> cubic solved by Omar Khayyam (text and Activity 5.9)<br />

• methods for finding local maxima and minima to help find the solutions <strong>of</strong> a<br />

cubic (Activity 5.10).<br />

Practice exercises<br />

1 A particular equation which was considered by al-Khwarizmi can be translated<br />

as follows.<br />

I one square and ten roots <strong>of</strong> the same equal thirty-nine.<br />

a Express this equation in a modern algebraic form.<br />

b Draw a square ABCD with side AB representing the 'root' <strong>of</strong> the equation.<br />

Extend AB to E and AD to F where BE = DF = 5, and complete the larger square<br />

on side AE. Extend the lines BC and DC to meet the larger square. Shade the areas<br />

representing the 'one square and ten roots <strong>of</strong> the same' in al-Khwarizmi's problem.<br />

c Hence find the positive solution to the equation.<br />

2 Explain why al-Khwarizmi's classification <strong>of</strong> quadratic equations does not<br />

include the case or cases in which squares and roots and numbers equal zero.<br />

3 Which <strong>of</strong> the Arabic numerals look most like those used in English texts today?<br />

What advantages and disadvantages can you see in the Arabic versions?<br />

4 Use al-Khwarizmi's method to solve x 2 + I2x = 64.<br />

5 Use Homer's method to solve x 2 + Ix = 60750.<br />

6 Write brief notes on Omar Khayyam's contribution to <strong>mathematics</strong>.<br />

7 Draw on your studies <strong>of</strong> Babylonian and Arab <strong>mathematics</strong> to write an account<br />

<strong>of</strong> two different approaches to problems which lead to quadratic equations.<br />

6 The approach <strong>of</strong> Descartes<br />

Chapter summary<br />

• a review <strong>of</strong> the legacy <strong>of</strong> Greek geometrical methods (Activities 6.2 and 6.3)

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