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circles, ellipses & hyperbolas and exact value triangles for spec
author
Andrew Lorimer
<andrew@lorimer.id.au>
Mon, 3 Dec 2018 23:07:53 +0000
(10:07 +1100)
committer
Andrew Lorimer
<andrew@lorimer.id.au>
Mon, 3 Dec 2018 23:07:53 +0000
(10:07 +1100)
spec/prelim.md
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b/spec/prelim.md
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spec/prelim.md
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spec/prelim.md
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-2,6
+2,9
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## Circular functions
## Circular functions
+![](../methods/graphics/exact-values-1.png){#id .class height=150px}
+![](../methods/graphics/exact-values-2.png){#id .class height=150px}
+
$\sin \theta$ - $y$-coord on unit circle
$\cos \theta$ - $x$-coord on unit circle
$\tan \theta = {\sin \theta \over \cos \theta}$
$\sin \theta$ - $y$-coord on unit circle
$\cos \theta$ - $x$-coord on unit circle
$\tan \theta = {\sin \theta \over \cos \theta}$
@@
-47,14
+50,31
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Sum of interior angles of $n$-sided polygon is $(n-2) \times 180^\circ$
- ![](graphics/segment-angles.png){#id .class width=40%} angles in the same segment of a circle are equal
- ![]()
- ![](graphics/segment-angles.png){#id .class width=40%} angles in the same segment of a circle are equal
- ![]()
+## Circles, ellipses and hyperbolas
+
+Standard form is $Ax^2+By^2+Cx+Dy=0$
+
+- if $A+B$ then circle
+- if $A>0$ and $B>0$ and $A\ne B$ then ellipse
+- if $A<0<B$ or $B<0<A$ then hyperbola
-##
Ellipses and hyperbola
s
+##
# Circle
s
-#### Ellipses
+$$(x-h)^2 + (y-k)^2 = r^2$$
+
+- centre $(h,k)$
+- radius $r$
+
+### Ellipses
$${(x-h)^2 \over a^2}+{(y-k)^2 \over b^2} = 1$$
$${(x-h)^2 \over a^2}+{(y-k)^2 \over b^2} = 1$$
-#### Hyperbolas
+- centre $(h, k)$
+- $x$-radius $a$
+- $y$-radius $b$
+- $\therefore \text{width}=2a, \quad \text{height}=2b$
+
+### Hyperbolas
$${(x-h)^2 \over a^2} - {(y-k)^2 \over b^2} = 1$$
$${(x-h)^2 \over a^2} - {(y-k)^2 \over b^2} = 1$$