Triantain

Diagram of a scalene triangle

Anns a h-uile triantan bidh na 3 ceàrnan a' dèanamh 180^\circ

Diagram of a scalene triangle with angles of 70°, 50° and an unknown angle marked as x°

x^\circ  = 180^\circ  - (70^\circ  + 50^\circ )

= 180^\circ  - 120^\circ  = 60^\circ

Triantan ionann-thaobhach

Ann an triantan ionann-thaobhach tha an aon fhaid anns na trì taobhan agus tha 60^\circ anns gach ceàrn.

Equilateral triangle

Triantan co-chasach

Ann an triantan co-chasach tha an aon fhaid ann an dà thaobh agus tha dà cheàrn co-ionann.

Diagram of an isosceles triangle with the two equal angles highlighted

Question

Tha triantan co-chasach san diagram gu h-ìosal. Dè an luach a tha aig a^\circ?

Isosceles triangle with a 70° base angle and a vertex angle marked as a°

a^\circ  = 180^\circ  - (70^\circ  + 70^\circ )

= 180^\circ  - 140^\circ  = 40^\circ