November 2009
Beginner
368 pages
8h 55m
English
Content preview from Head First 2D Geometry
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58 Chapter 2
similar triangles have the same angles
Similar triangles don’t just look the same
Similarity is a key piece of geometry jargon. If two shapes are similar, then
they don’t just look alike, one is an exact scaled version of the other. This
means that they have the same (equal) angles.
But don’t take our word for it…check that it all adds up:
Line part way up
the triangle
Tick marks to show that
our line is parallel
These triangles are similar. In
geometry terms, we don’t just
mean they kinda look the same.
Similar triangles
don’t have to be
the same way up.
86°
53°
41°
86°
53°
41°
86
o
41
o
53
o
41
o
53
o
86
o
41°
53°
86°
Take a big triangle, and draw
a line part way up the triangle,
parallel with the base.
1
This creates a mini triangle
which shares the angle at the
peak of the big triangle.
2
you are here 4 59
similarity and congruence
Using what you know about parallel lines and the F pattern, find the two
mystery angles to complete the mini triangle you’ve created.
If the line is drawn parallel to one of the other sides, do you still end up with the
same angles in your mini triangle?
Remember the F, N, Z patterns
from chapter 1? No? Check out
page 40.
?
?
86
o
41
o
53
o
?
?
41
o
86
o
53
o
41
o
86
o
53
o
?
?
60 Chapter ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.