MATHS REVISION ANGLES AND LOCI 0.0 / 5 MathematicsAngles2D and 3D shapeGCSEEdexcel Created by: 41sha333Created on: 16-03-17 19:08 MATHS -- GEOMETRY ANGLE BASICS acute angles : sharp and pointy angles which are less than 90` obtuse angles : wider angles (between 90` and 180`) right angles : square corners(90`) DRAWING ANGLES WITH A PROTRACTER : 1. Draw a base line 2.if the angle is an acute angle then you can make sure the protractor's 0 is facing inwards. 3. if it is a small angle use the outside scale. 1 of 5 MATHS -- GEOMETRY (2) GEOMETRY RULES: 1. Angles in a triangle = 180' -- a+b+c=180' 2. Angles on a straight line add upto 180`-- a+b+c=180' 3. Angles in a quadrilateral add up to 360' -- a+b+c+d=360' 4. Angles round a point = 360' 5.Exterior angle of a triangle = sum of opposite interior angles. a+b=d 6. Isosceles triangles have 2 sides the same and 2 angles the same . 2 of 5 MATHS -- GEOMETRY (3) PARALLEL LINES Alternate angles: alternate angles are the same they are found in a Z shape. Vertically opposite angles : vertically opposite angles add up to 180' they are found in a C or U shape Corresponding Angles: corresponding angles are the same.They are found in an F shape. Example ; find the angle x There is a corresponding angle that is 115' what is x ? Its the same ! 3 of 5 MATHS -- GEOMETRY (4) INTERIOR AND EXTERIOR ANGLES For any polygon (regular or irregular) sum of exterior angles =360' interior angles =180' - exterior angles for regular polygons only : exterior angles = 360/n (number of sides) SUM OF INTERIOR ANGLES the formula for all polygons: SUM OF ANGLES= (n-2x180') E.G For a pentagon. pentagon = 5 sides Sum of interior angles=(5-2)x180'=540' 4 of 5 MATHS -- GEOMETRY REVISON SUMMARY QUESTIONS: 1. Give an example of an acute angle, obtuse and reflex angle (3) 2. What do the angles in a quadrilateral equal to? (1) 3. What type of angles do you find a Z shape on parallel lines? (1) 4.Work out the size of an exterior angle and an interior angle of a regular decagon (10 sided shape) (2) 5.What is the sum of the interior angles in a hexagon and heptagon (2) 5 of 5

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