When learning mathematics, we often deal with mathematical symbols such as "+","-"and "=". Over time, we became good friends with them. But do you know the origin of these friends? Speaking of age, the plus sign "+"and the minus sign "-"are big brothers. 500 years ago, there was a German mathematician named Weidemann, who added a vertical bar to the horizontal line to indicate the increase. Remove a vertical bar from the plus sign to indicate reduction. So the plus sign "+"and the minus sign "-"were born. But it was not until the Dutch mathematician Heuck started in 15 14 that they were officially recognized as symbols of addition and subtraction. The equal sign = is younger than both of them. More than 400 years ago, the British scholar Cod.