A rectangle which can be divided into a square and a smaller similar rectangle has length and breadth in the Golden Ratio
Back in the classroom after Easter for Mechanics 1 consolidation and revision.
Carr’s 626, in his magical book for Edwardian mathematical autodidacts, provides summary of general solutions for trigonometrical equations useful to STEP and A level students.
Friendly triangles – good visual method for memorising trig ratios of 30, 45 and 60 degree angles. Known for thousands of years as per the Babylonian tablet