# Maths Descriptions for Students

## RIGHT-ANGLE TRIANGLE A right triangle has one right-angle. The side opposite the square of any right angle triangle is called the hypotenuse. To find the hypotenuse, use the formula , where c = the hypotenuse,
a = the base of the triangle and b = the height of the triangle. The square is the 90° angle in the right triangle.

Example: A right angle triangle has a height of 5 cm and a base of 3 cm, find the hypotenuse.  (note: answer is rounded to the nearest hundredth)

## HEXAGON A hexagon is a polygon with six sides. A polygon is a closed plain figure bounded by three or more straight sides that meet in pairs in the same number of vertices, that do not intersect other than at these vertices.

Vertices is the plural of vertex. Vertex means the point opposite the base of a figure or the point of intersection of two sides of a plain figure or angle.

To find the area of a hexagon use the formula A = 3/2 xx 3
Where A = area and r = radius.

The radius is the straight line joining the centre of a circle or sphere to any point on the circumference or surface. The length of this line is usually denoted by the symbol r.

## OCTAGON An octagon is a polygon with eight sides. A polygon is a closed plain figure bounded by three or more straight sides that meet in pairs in the same number of vertices, that do not intersect other than at these vertices.

Vertices is the plural of vertex. Vertex means the point opposite the base of a figure or the point of intersection of two sides of a plain figure or angle.

To find the area of an octagon use the formula A = 2 x x 2
Where A = area and r = radius.

The radius is the straight line joining the centre of a circle or sphere to any point on the circumference or surface. The length of this line is usually denoted by the symbol r.

## CIRCLE A circle is a closed plane curve where every point is equally distant from the centre.

To find the area of a circle use the formula A = p x
Where A = area, p= pi (3.14) and r = radius.

## RADIUS The radius is the straight line joining the centre of a circle or sphere to any point on the  circumference or surface. The length of this line is usually denoted by the symbol r.

EXAMPLE

Complete the table below using the formula;  y = 5 x + (80 ÷ 5) - 3

Solution...

Y = (5 × -3) + (80 ÷ 5) - 3 = -2
Y = (5 × -2) + (80 ÷ 5) - 3 = 3
Y = (5 × -1) + (80 ÷ 5) - 3 = 8
Y = (5 × 0) + (80 ÷ 5) - 3 = 13
Y = (5 × 1) + (80 ÷ 5) - 3 = 18
Y = (5 × 2) + (80 ÷ 5) - 3 = 23
Y = (5 × 3) + (80 ÷ 5) - 3 = 28

 x -3 -2 -1 0 1 2 3 y -2 3 8 13 18 23 28

 When the hypotenuse and one side of a right-angle triangle is known, you can find the length of the unknown side by using the Pythagoras theorem. To do this, follow the steps below. Square the hypotenuse.  6×6=36. Square the other known side.  5×5 = 25. Subtract the known smaller side from the hypotenuse 36-25=11 Square root the result of the subtraction.  √ 11 = 3.32 rounded to the nearest hundredth.  3.32 is the length of the unknown side. Or examine the example solution below: 