Answer:
18. Further developed their ideas in geometry, trigonometry, and algebra. To simplify mathematics, they used the decimal number system and encouraged its adoption as the world's standard number system
19. The quran influenced Islamic art because the quran banned the worship of idols, so muslim leaders forbid artists to potray God or human figures in religious art, which gave Islamic art a clear style, mosaic, and calligraphy of the Quran.
20. The Safavids benefited from their geographical position at the centre of the trade routes of the ancient world. They became rich on the growing trade between Europe and the Islamic civilisations of central Asia and India.
21. The only answer is the Ottoman Empire. It is the only Muslim Empire that stayed relevant into the 19th century while the rest of the Arab world stagnated both culturally and technologically. They of course became Turkey which is secular and eventually adopted a Pro-European political stance but for a while they were Europe’s greatest threat.
22. After Muhammad's death in 632, the teachings of Islam spread rapidly to many people and places in the Middle East.
23. 655 C.E. Islam begins to spread throughout North Africa. 661 C.E. Imam Ali is killed, bringing to an end the rule of the four "righteous caliphs": Abu Bakr, Umar, Uthman, and Ali. This also marks the beginning of the Umayyad rule. 711 C.E. Muslims enter Spain in the west and India in the east
