A triangle is a polygon with three angles and three sides. We can classify them:

- According to their sides:

   · Scalene: no equal sides

   · Isosceles: two equal sides


   · Equilateral: three equal sides


- According to their angles:

   · Acute: three acute angles (less than 90o)


   · Right-angled: one right angle (90o)


    · Obtuse: one obtuse angle (more than 90o)




Exercise: classify these triangles:







Solutions: a) Scalene obtuse triangle; b) Isosceles right-angled triangle; c) Equilateral acute triangle

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