#209 Congruency vs similarity
#233 Basic triangle theorems
#232 Congruency and triangles
#249 Some geometry basics
#251 Solving as a function of x in an isosceles triangle
#253 Using circle geometry to prove congruency
#254 Congruency of triangles with follow up questions
#255 Pythagoras and area of a trapezium
#256 Using circumference to calculate area
#257 Doubling the length of a rectangle to see how area changes
#260 Similarity of triangles and calculating the length of a side