triangle

A triangle is a polygon with three vertices and three sides.

There are different types of triangles:

    • equilateral

    • isosceles

    • scalene

    • right-angled.

The interior angles of any given triangle add up to a total of 180°.

There are two formulas for calculating the area of a triangle. One formula is:

    \text{Area} = \dfrac{1}{2} \times \text {Base} \times \text{Height}

               = \dfrac{1}{2} \times b \times h

The base b represents the length of one of the triangle’s sides and the height h represents the distance from the base to the opposite vertex. Note that the height is measured at a right angle to the base.

The other formula is:

    \text{Area} = \dfrac{1}{2} \times a \times b \times\sin C

In this formula a and b represent the length of two of the triangle’s sides and C represents the angle between these sides.

It is possible to use several methods to decide whether two triangles are similar or congruent.

If we have a right-angled triangle, we can use Pythagoras’ theorem or trigonometry methods to discover missing lengths or angles.

In a triangle with no right angles, we can use the sine rule or the cosine rule to discover missing lengths or angles.