In mathematics, a circled X is actually the Phoenician letter Teth. Find out what a circled X means in math with help from an experienced mathematics educator in this free video clip.

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In mathematics, a circled X is actually the Phoenician letter Teth. Find out what a circled X means in math with help from an experienced mathematics educator in this free video clip.

Part of the Video Series: Math Lessons & Tips

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Hi, my name is Marija, and today I'm going to tell you what a circle with an X drawn through it means. So, this symbol right here is actually the Phoenician letter Teth. And this symbol is where the current theta that we use a lot in Math, in Geometry was derived from. So, this is a symbol that many of us know as theta which is the eighth letter of the Greek alphabet and this was derived from the old Phoenician letter Teth which looks like the symbol of a circle with an X through it. And theta is use a lot in Geometry and Trigonometry to represent angles that are unknown. So, much like we use an X to represent sides and lengths that we don't know, usually if you have a triangle or an angle and we don't know what it is, we use the letter theta to represent that amount of angles. So, this letter theta has its history and the letter Teth which looks like a circle with an X symbol in it.