Find the area of the black regionFind the area of the black region accurate up to 3 decimal places. (A=?, a=20, b=10)
Correct answers: 23
The first user who solved this task is Sanja Šabović.
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Charles Joseph Van DepoeleBorn 27 Apr 1846; died 18 Mar 1892 at age 45.Belgian-American inventor who was a pioneer in railway, electric lighting, and mining work, with more than 100 patents on electrical inventions. He emigrated to the U.S. in 1869. While experimenting with electric motors in Detroit (1874) he established the practicality of railway cars running on electricity. He invented an electric generator (1880), and exhibited an operating electric streetcar at the Chicago Exposition of Railway Appliances (1883). He designed electric streetcar systems for several cities. In 1888, he sold his electric railway patents to Thomson-Houston Electric Company of Lynn, Mass. He died four years later, at age 46. His other patents include: arc lamp (1870), coal-mining machine (1891), gearless electric locomotive (1894).«