Question

Point D(-3.5) is a vertex of triangle DEF.After a rotation of the triangle about the origin, D' is located at (3,-5).Which of the following was the rotation of the triangle?

Answer 1

Answer: 180 degrees

note: it doesn't matter if its clockwise or counterclockwise when it comes to 180 degree rotations.

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Explanation:

The rule for 180 degree rotations is

(x,y) ---> (-x, -y)

So the x and y coordinates flip in sign from positive to negative, or vice versa.

Point D ' (-3, 5) rotates to D ' (3, -5) following this rule

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A further detailed break down might look like this

x = -3 becomes -x = -(-3) = 3

y = 5 becomes -y = -5

(-3, 5) ----> (3, -5)