IGCSE Maths / Transformation and similarity

Proving triangles are congruent revision notes

Edexcel International GCSE Maths (4MA1), chapter 14: Transformation and similarity, specification point 4.2g. Part of the full course.

Watch the video lesson · IGCSE Maths past papers

Congruent triangles have exactly the same shape and size. To prove two triangles are congruent, show three matching pairs are equal, give a reason for each pair, then state the congruence condition with the vertices in the correct order.

More lessons in Transformation and similarity

• Lines of symmetry and rotational symmetry
• Equations of common mirror lines
• Reflecting a shape in a line
• Reflecting in y = x and y = -x
• Finding the mirror line from object and image
• What defines a rotation
• Rotating a shape about a point
• Positive and negative rotation angles
• Rotating about a point not on the shape
• What defines a translation
• Translating a shape
• Column vectors in translations
• Congruence under transformations
• Describing a single transformation fully
• Combining two transformations
• What defines an enlargement
• Similarity under enlargement
• Enlarging from a given centre
• Fractional scale factor enlargements
• Finding the centre of enlargement
• Conditions for congruent triangles
• Similar shapes: corresponding lengths
• Area scale factor
• Volume scale factor
• Similar solids, mass and capacity
• Similar shapes problem solving