We saw earlier the proof and derivation for the area of a triangle (right, acute, obtuse angled triangles). We’ll now look at some examples of area of triangle calculations.

**Example 1**:

Area of triangle =

=

= 9 cm^{2}

**Example 2**:

=

= 27 cm^{2}

**Example 3**:

=

= 21 mm^{2}

**Example 4**:

Area of shape = area of rectangle A_{1} + area of triangle A_{2} _{}

A_{1} = l x b

= 8 x 5

= 40 cm^{2}

A_{2} =

= (height of triangle = 12 – 5 = 7 cm)

= 28 cm^{2}

So area of shape = A_{1} + A_{2}

= 40 + 28

= 68 cm^{2}

**Example 5**:

Area of shape = area of rectangle A_{1} – area of triangle A_{2}

A_{1} = l x b

= 11 x 7

= 77 mm^{2}

A_{2} =

=

= 15 mm^{2}

So area of shape = A_{1} – A_{2}

= 77 – 15

= 62 cm^{2}