Bound : A bound refers to a level that is not exceeded by a function or sequence (upper bound) or a level that a function or sequence does not go below (lower bound). For example the function $f(x)=x^2$ has a lower bound of 0 but no upper bound. The function $f(x)=\sin x$ has an upper bound of 1 and a lower bound of -1.

Cos : The cosine of an angle $0\leq\alpha\leq 180^{\circ}$ or $\cos \alpha$ is defined by finding a right triangle with angle $\alpha$ and dividing the length of the leg adjacent to $\alpha$ by the length of the hypotenuse. For arbitrary angles the cosine function can be extended in a periodic way by inscribing the right triangle in a circle. The cosine can be used to calculate unknown side lengths in a triangle via the cosine law and in the case of right triangles via its definition. The Pythagorean theorem implies that $\cos^2 \alpha+\sin^2 \alpha=1.$

Even : Even can refer either to an even function or an even number.

Function : A function is a mapping in which every element in one set is mapped to exactly one element of a second set. Most often the mapping is described using a rule. For example the function $f(x)=x+1$ maps 2 to 3 and -1 to 0.

Graph : The graph of a function is the set of points $\{(x,f(x))\}$ that can be blotted in a coordinate system.

Odd : In mathematics odd can refer either to an odd function or an odd number.

Division : Division is the mathematical operation that divides objects equally into groups. More generally $x\div y$ is defined as the number that if multiplied by $y$ equals $x.$

Standard algorithm : By standard algorithm we refer to any one of the algorithms that are commonly taught at school to add, subtract, multiply or divide multi-digit numbers such as long division and partial products multiplication.

Angle : If two line segments (or rays) both start at a common point the opening between the two line segments is called an angle. The common point is called vertex of the angle. The size of an angle is measured in degrees.

Equilateral : A polygon that has side lengths that are all equal is called equilateral polygon.

Equilateral triangle : An equilateral triangle is a triangle with three sides of equal length. An equilateral triangle is also equiangular and has interior angles of $60^{\circ}.$

Isosceles triangle : An isosceles triangle is a triangle in which two side length are the same. The two angles at which these two sides meet the third side are the same.

Obtuse angle : An obtuse angle is an angle bigger then $90^{\circ}.$

Obtuse triangle : An obtuse triangle is a triangle that has one obtuse angle.

Right angle : A right angle is an angle equal to $90^{\circ}.$

Right triangle : A right triangle is a triangle that has a right angle. The sides that form the right angle are called legs, the third side is called hypotenuse. The area of a right triangle is half the product of the lengths of the two legs. The Pythagorean theorem is an important theorem for right triangles that allows to calculate the third side of a right triangle given the other two.

Triangle : A triangle is a polygon with three corners and three sides. You can calculate the area of a triangle by multiplying half the length of the base by the height on that base. The sum of the interior angles in a triangle is always $180^{\circ}.$