median
don steward
mathematics teaching 10 ~ 16

Showing posts with label perpendicular lines. Show all posts
Showing posts with label perpendicular lines. Show all posts

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


Tuesday, 5 February 2019

CBSE lines and perpendiculars questions

these are or are similar to CBSE (India) questions
mainly for Y10 students

the powerpoint is here




GCSE line questions

these are based on recent Edexcel questions
they involve finding perpendiculars

the powerpoint is here






Thursday, 23 November 2017

two tangents meet on the y-axis

these tasks are my versions of a five triangles tweeted task (on July 19th 2017)
their tweets are now protected






Friday, 11 November 2016

trapezium area bisected

intended to practice using a method for calculating the area of a trapezium
the powerpoint is here


the space underneath each shape is for students to record (show) their calculations




























the shapes should be congruent:

creating half of the trapeziums has an easily spotted rule

why does this rule work?













this offers an introduction to perpendicular gradients (or rotations of 90 degrees)

Thursday, 20 October 2016

triangles cut into triangles

the main purpose of this work is to provide a focus on triangle areas
particularly with same bases and equal heights (Euclid I. 37)
but there are various optional spin-offs:
  • perpendicular lines
  • surd lengths
  • length and area ratios of similar shapes



questions for the triangles above


the team at Puntmat (@puntmat) have found 8 ways (so far) to cut up a 3 by 6 right triangle into three equal areas (i.e. non-congruent thirds):


their post on fractions of geometrical shapes contains many good exercises

many thanks to them











dividing unequally:

Thursday, 31 March 2016

quadratic graph properties

some of the properties of  y = x ^ 2
only considering integer points

work developed with David Wells

a ppt is here

several interesting applications of:
  • straight line graphs (the chord equations are all neat)
  • mid-points
  • tangents (are parallel to a family of chords)
  • perpendicular line equations