The major contribution of the Islamic Age to the history of medicine was the establishment of hospitals, paid for by the charitable donations known as Zakat tax. Muslims made great technical and scientific advancements during the years 750 to 1200 CE. Examples of Muslim advancements in mathematics and medicine are spherical trigonometry and the treatment of eye diseases. This era is known in the Muslim world as the Islamic Golden Age. Muslim medicine is much more advanced than the medicine practiced by other cultures of the time. During the Middle Ages, Muslims made many intellectual contributions. They built upon the knowledge obtained by previous cultures. Much of Islam's scientific advances were based on the scientific knowledge of the Greeks. Muslim scholars were very skilled in the field of astronomy and developed a calendar that was quite accurate. Which they needed to keep track of religious observances. The astrolabe was an instrument that had been used by the ancient Greeks to calculate the position of the sun and stars. Muslim astronomers improved the astrolabe around 850 A.D. With the use of the astrolabe, Muslim geographers were able to calculate the size and circumference of the Earth. Muslim scholars created algebra and trigonometry. Chemistry was created by Muslim scholars. Muslim mathematicians created trigonometry because astronomers needed a way to calculate the distance from earth to objects in the sky.
Income taxes are the cornerstone of Georgia's revenue system, accounting for half of all state funds. Sales taxes are the second largest revenue source, representing slightly less than a quarter of annual collections
