The three corners of a triangle are sitting on a circle. The angles
are called Angle A, Angle B and Angle C. The dot in the middle of
the circle shows the centre. The counter is measuring the size of
Angle A in degrees. What is the smallest Angle A can be? What is
the largest Angle A can be? What else do you notice about Angle A
as you move the corners of the triangle around the circle?
Getting an Angle
Stage: 3 Challenge Level:
Remember that folding an equilateral triangle in half gives you
a 30-60-90 triangle and the ratios of the lengths of the sides.
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice. More information on many of our other activities
can be found here.