2.2 Linear Transformation in Geometry Example. 1 Consider a linear ...

2.2 Linear Transformation in Geometry Example. 1 Consider a linear ... 2.2 Linear Transformation in Geometry Example. 1 Consider a linear ...

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Example. 5 Give a geometric interpretation of the linear transformation. T (x) = a −b b a Rotation-dilations A matrix with this form a −b b a denotes a counterclockwise rotation through the angle α followed by a dilation by the factor r where tan(α) = b a and r = a2 + b2 . Geometrically, ✻ ✡ α ✡ ✡ ✡ ✡✡✡✡✣ ✲ a b = x r cos α r sin α ✲ 4

[Shears] Example. 6 Consider the linear transformation T (x) = 1 1 2 0 1 To understand this transformation, sketch the image of the unit square. x 1 1 2 Solution The transformation T (x) = 0 1 is called a shear parallel to the x1-axis. 5 x

<strong>Example</strong>. 5 Give a geometric <strong>in</strong>terpretation<br />

of the l<strong>in</strong>ear transformation.<br />

T (x) =<br />

<br />

a −b<br />

b a<br />

Rotation-dilations A matrix with this form<br />

<br />

a −b<br />

b a<br />

denotes a counterclockwise rotation through<br />

the angle α followed by a dilation by the factor<br />

r where tan(α) = b <br />

a and r = a2 + b2 . Geometrically,<br />

✻<br />

✡ α<br />

✡<br />

✡<br />

✡ ✡✡✡✡✣<br />

✲<br />

a<br />

b<br />

<br />

<br />

=<br />

<br />

x<br />

r cos α<br />

r s<strong>in</strong> α<br />

✲<br />

<br />

4

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