Basic Geometric Facts Learning Pages

Your Turn!!

Sketch a copy of triangle ABC above and without looking at the explanation given, explain in simple terms why the angle sum of triangle ABC is 180°.

Check back to the explanation, and type ‘yes’ if you have successfully done this. π + − ÷ × < > ≤ ≥ π

RAPID TEST

With reference to the diagram above, fill in the gaps to explain why the angle sum of the triangle must be 180°:

A = π + − ÷ × < > ≤ ≥ π (Z-angles) and B = π + − ÷ × < > ≤ ≥ π (Z-angles)

C + D + E = π + − ÷ × < > ≤ ≥ π ° (angles on a straight line)

Replacing A for π + − ÷ × < > ≤ ≥ π and B for π + − ÷ × < > ≤ ≥ π gives A + B + C = 180°, as required.

RAPID TEST

Fill in the gaps to explain one of the properties of quadrilaterals (4-sided closed shapes):