don steward
mathematics teaching 10 ~ 16

Friday, 6 March 2020

grid geometry perpendiculars

it seems helpful to consider (and then define) perpendicularity in terms of a 'rotated' vector (through 90 degrees)

equal lengths can be established from the diagonals of rectangles (or, later, by pythagoras)

a powerpoint is here

show that the diagonals of kites cross at right angles

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