# Ptolemy trigonometry contribution. Ptolemy's sum and difference formulas 2019-01-22

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## Contributions to Society

He determined the first three of these chords using the figure below with the following proof. By the end of the 10th century trigonometry occupied an important place in astronomy texts with chapters on sines and chords, shadows tangents and cotangents and the formulae for spherical calculations. This classical theorem has been proved many times over. Until about the 16th century, trigonometry was chiefly concerned with computing the numerical values of the missing parts of a triangle or any shape that can be dissected into triangles when the values of other parts were given. Ptolemy expanded the table of chords that had originated with Hipparchus, calculating them at intervals of 1 degree.

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## Ptolemy

In several fields his writings represent the culminating achievement of , particularly his of the now known as the. And so, problems in trigonometry have required new developments in synthetic geometry. The fundamental assumption of the Almagest is that the apparently irregular movements of the heavenly bodies are in reality combinations of regular, uniform, circular motions. Equivalence of the Table of Chords and a table of sines Given a circle whose diameter and circumference are divided into 120 and 360 parts respectively, Ptolemy was able to calculate the corresponding chord length for every central angle up to 180° in half-degree intervals. Al-Khwarizmi's version of Zij used Sines and Versines, and developed procedures for tangents and cotangents to solve astronomical problems. Regiomontanus died during an outbreak of plague in Rome in 1476. Any j … ob dealing with any type of waves sound waves, the pattern that the tide follows has to know about Trigonometric Functions.

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## Ptolemaic Astronomy in the Middle Ages

The book was written principally as a contribution to the science of astronomy, but we now recognise Regiomontanus as the first European scholar who treated trigonometry as a theoretical science, setting out a series of logical propositions and proofs in the style of Euclid. This new religion was a combination of both Greek and Egyptian influences, although the Egyptians saw it as more Greek than Egyptian. Recall that the sine of an angle is half the chord of twice the angle. He computed the chord of 72°, an central angle of a pentagon, a constructable angle. By the 10th century Cordoba was said to have equally good libraries and educational establishments as Baghdad, and the cities of Cordoba and Toledo became centres of a flourishing translation business. The work we have of his, Commentary on Aratus and Eudoxus , was written in 3 books as a commentary on 3 different writings. Ptolemy included information about the Celestial sphere in two of his books.

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## Mathematical Discoveries

Technology has rendered the work of such mathematicians superfluous in much the same way the Almagest obliterated all twelve volumes of Hipparchus. His treatise helped to spread trigonometry in Europe in the 13th century, and his theorems were used by the astronomers who compiled the influential Libro del Cuadrante Sennero Book of the Sine Quadrant under the patronage of King Alfonso X the Wise of Castille 1221-1284. Ptolemy made hismost original contribution by presenting details for the motions of each of the planets. He realized that at that moment the sun appeared at the zenith, directly above the well. He lived in Alexandria in the Roman province of Egypt during the 2nd century.

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## History of trigonometry

Then he measured the shadow of an obelisk of known height in Alexandria, on the summer solstice at noon, and calculated the circumference of the earth. Brahe's data was used by Kepler to develop his laws of planetary motion, determining that the Earth had an elliptical orbit around the Sun. It has a short proof in. When Europeans translated the Arabic works into Latin they translated jaib into the word sinus meaning a fold in Latin. Other writers followed, and soon the word sinus, or sine, was used in the mathematical literature throughout Europe. After dividing by 4, we get the addition formula for sines.

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## Ptolemy

This one can be found in Advanced Trigonomentry by C. Ptolemy was preeminently responsible for the geocentric cosmology that prevailed in the and in Europe. They used the ecliptic as their base circle in the celestial sphere, that is, the crystal sphere of stars. This was based entirely on comparing the results of his calculations with earlier values. He recorded the positions and brightness of about 850 bright stars, and his classification system, magnitude of brightness, is still used today. Hence, a table of values for chords in a circle of fixed radius is also a table of values for the sine of angles by doubling the arc.

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## Trigonometry

That is, if you want to know the remaining angle and the remaining two sides, all you have to do is lay out the given side and the two angles at its ends, extend the other two sides until they meet, and you've got the triangle. During the , while Europe was plunged into darkness, the torch of learning was kept alive by and scholars living in Spain, Mesopotamia, and Persia. Only about twenty of these works now survive, and only about a dozen of these have been published. Stars were spherical because of the sphere's perfection, thusallowing stars to keep their position. There are 12 zodiac signs, and each are dedicated to different times of the year.

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## Ptolemy's sum and difference formulas

In contrast, tangent and cotangent properties were derived from the measurement of shadows of a gnomon and the problems of telling the time. Much of the material in The Almagest was already known to Greek astronomers. Greek astronomers had long since introduced a model of the universe with the stars on the inside of a vast sphere. Their extension to nonperiodic functions played a key role in the development of in the early years of the 20th century. Such calculations distinguish trigonometry from , which mainly investigates qualitative relations. Based on his observations of solstices and equinoxes, Ptolemy then found the lengths of the seasons and, based on these, he proposed a simple model for the sunwhich was a circular motion of uniform angular velocity, but the earth was not at the centre of the circle but at a distance called the eccentricity from thiscentre. A highly influential scientific text, its geocentric model accepted for more than 1200 years from its origin.

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## Biography of Claudius Ptolemy

For example, the triangle contains an angle A, and the of the side opposite to A and the side opposite to the right angle the hypotenuse is called the sine of A, or sin A; the other trigonometry functions are defined similarly. Even though his brilliance is widely accepted, scholars in the recent centuries have cast doubts over some of his astronomical observations. He provided many new proofs and showed how they could be used to solve many problems more easily. Hipparchus not only gave observational data for the moon which enabled him to compute accurately the various periods, but he developed a theoretical model of the motion of the moon based on epicycles. Knowing the length of a single base line enables the surveyor to define the other elements of the triangle by measuring the angle to the inaccessible points from accessible points. This was a considerable advance in Spherical Trigonometry that enabled the calculation of the correct direction for prayer the quibla and was to have important applications in Navigation and Cartography. The modern trigonometrical functions are sine, cosine, tangent, and their reciprocals, but in ancient Greek trigonometry, the chord, a more intuitive function, was used.

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