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**5.**invented zero**7.**those angles that sum up to 180 degrees**11.**father of mathematics**12.**longest side in a right-angled triangle**15.**When the sum of two angles is equal to 90 degrees**16.**a resultant number when one number is divided by the other number**19.**if the lines are parallel**20.**An angle which is measuring less than 90 degrees

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**1.**A constant is a value or number that never changes in expression**2.**when 2 figures shape is same, but size is proportional**3.**U-shaped curve that is drawn for a quadratic function**4.**a line that passes through two lines in the same plane at two distinct points in the geometry**6.**a number or quantity placed with a variable**8.**A line that touches the circle at a single point**9.**if the lines intersect at a point**10.**an alphabet or term that represents an unknown number or unknown value or unknown quantity**13.**instrument used for meaning angles with a rotating telescope**14.**when 2 figures are in equal shape and size**17.**triangle that has at least two sides of equal length**18.**any angle greater than 90°