Eisimpleir

Obraich a-mach farsaingeachd an triantain cho-chasaich seo:

Diagram of an isoceles triangle with two sides 14.5cm long, and a 12cm base

Freagairt

Farsaingeachd triantain \( = \frac{1}{2} \times \text{bonn} \times \text{àirde}\)

Tha fios againn gu bheil \(12\,cm\) sa bhonn, ach chan eil fios againn air an àirde.

Obraichidh sinn a-mach an àirde le bhith a' roinn an triantain cho-chasaich na dhà thriantan cheart-cheàrnach, agus an uair sin a' cleachdadh Teoram Phythagoras le aon dhiubh.

Diagram of an isoceles triangle being divided in two.

\[{\text{à}^2} = {14.5^2} - {6^2}\]

\[{\text{à}^2} = 210.25 - 36\]

\[{\text{à}^2} = 174.25\]

\[\text{à} = \sqrt {174.25}\]

\[\text{à} = 13.20\,(gu\,2\,id.)\]

Tha fios againn a-nis air àirde an triantain agus faodaidh sinn seo a chleachdadh airson a dhol air ais agus farsaingeachd an triantain cho-chasaich obrachadh a-mach.

Farsaingeachd triantain \( = \frac{1}{2} \times \text{bonn} \times \text{àirde}\)

Farsaingeachd triantain \( = \frac{1}{2} \times 12 \times 13.20\)

Farsaingeachd triantain \( = 79.2\,c{m^2}\)