a ppt is here
sum to 90 degrees: complementary
sum to 180 degrees : supplementary
sum to 360 degrees: explementary
sum to 45 degrees: halfrightlementary (or anything else...)
this is part of a series of tasks involving a square dot grid and expressing an angle as arc tan (fraction)
in this case, it is exploring what two angles sum to 45 degrees
these were used in several tasks, part of a session at Anne Watson and John Mason's house looking at the topic of 'angle'