toy treasures - arvind gupta (60 kb doc)

PAPER PROTRACTORTake a 10-cm x 10-cm piece of square paper(ABCD) Fig (1).Fold its middle line EF Fig (2).Fold corner B and move it up and down onmidline EF until line BA passes through theleft - hand corner A Fig (3).Crease AG, Fig (3). By doing this angle AGBwill become exactly 60-degrees.Now consider triangle ABG; as angle ABGis right angled - being the corner of thesquare, and as angle AGB is 60-degrees, so theremaining angle BAG will be 30-degrees Fig(4).Now fold the lower triangle along line BGand tuck it below triangle ABG Fig (5).Bring edge AD and AB together so as to bisectangle DAB (30-degrees) into half.Now angle PAB will be 15-degrees.As angle ABP is a right angle - being a cornerof a square so the remaining angle APB willbe 75-degrees Fig (6).Now we have a beautiful paper protractorwith angles of 15, 30, 45, 60, 75, 90 degreesmarked on it.Corners P (75-degrees) and G (60-degrees)can always be opened and doubled up to makeangles of 150-degrees and 120-degrees.So, next time if you forget your geometry boxthere isn’t much to worry about.Just fold a paper protractor.