2All About SurdsA surd is a number which is written with a root sign and cannot be simplified e.g. 3 , or 17Trying to write down the exact number as a decimal is impossible because surds are irrational numbers and therefore the decimal part ‘continues forever’, without repeating.
11Side Lengths of Squares Knowing the areas, can you find the length of the side of each square?
12Side Lengths of Squares 1√22√ 53√ 845√ 10√ 17√ 13
13Side Lengths of Squares One of these expressions can be simplified.You might notice that the larger square is an enlargement of the smaller one – twice the side length (although 4 times the area).If the side length of the smaller oneis √2, the larger one must be 2√2
14Side Lengths of Squares This means that 8 =2 28 = 4×28 = 4 × 28 =2 2
15Lengths of LinesCan you find the length of each line on the next slide?Simplify where possible.Hint: think about each line as the hypotenuse of a right-angled triangle
22Teacher notesIn this edition, the focus is on surds and familiarisation with lengths of sides in right angled triangles involving surds, culminating in playing a new mathematical game. Students should have previously used Pythagoras’ theorem. Some parts of the activity are suitable for Foundation GCSE students, others for Higher GCSE or AS students Tilted squares Slide 4 The class will need to decide whether position and orientation are ‘important’ in this task. With rotations, translations and reflections of a square considered to be ‘the same’ there are 11 different squares that can be found.
23Teacher notesAreas of squares Slides 8 & 9 Students can show their methods for finding the area using the ‘ink annotation’ tool (which becomes visible when the pointer is allowed to hover over the bottom left of the PPT slide). It is worth flagging up Pythagoras theorem if no-one comes up with it. You might ask which method is the most time efficient.
24Teacher notesSlide 9 Students can show their methods for finding the area using the ‘ink annotation’ tool (which becomes visible when the pointer is allowed to hover over the bottom left of the PPT slide). They might divide the square up into smaller shapes, enclose the square or use Pythagoras’ theorem.
25Teacher notesSide Lengths of squares Slides 11& 12 Students should realise that once they have the area of the square, the side length is simple the square root of it. Slide 13 Simplifying roots. Lengths of lines Slides 16 & 17 It’s helpful to point out where lines pass through dots, linking to the idea of enlargement i.e. the dots on g split the line into 3, making it 3 times bigger than a 2 line.
26AcknowledgementsSquare Root of 2 to places Accessed 29/10/14 nrich Tilted Squares ‘checker’