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Geometry and Measurement Videos 87 videos

SAT Math 1.1 Geometry and Measurement
719 Views

SAT Math 1.1 Geometry and Measurement. What is the circumference of the circle?

SAT Math 1.2 Geometry and Measurement
246 Views

SAT Math: Geometry and Measurement Drill 1, Problem 2. If A = (0, 4), B = (-3, 2), and C = (1, 0), which point is in the interior of angle ABC?

SAT Math 1.3 Geometry and Measurement
231 Views

SAT Math 1.3 Geometry and Measurement. Find the length of CE.

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SAT Math 4.2 Geometry and Measurement 278 Views


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Description:

SAT Math 4.2 Geometry and Measurement

Language:
English Language

Transcript

00:02

Here’s your shmoop du jour, brought to you by rotating triangles.

00:10

Triangle ABC is rotated 90° counterclockwise about the origin, then reflected over the y axis.

00:17

What are the new coordinates of C?

00:19

Here are the potential answers...

00:24

Who knows why we’re rotating and reflecting this triangle…

00:27

…maybe it was getting stir crazy and wanted a change of scenery.

00:30

Whatever the reason, this problem tells us that we must first rotate the sucker 90 degrees about the origin…

00:36

…and then reflect it across the y axis.

00:40

When we rotate the triangle about the origin,

00:42

that means that we have to picture the entire thing on a hinge…

00:46

…and that hinge is at zero, zero.

00:48

…we just have to imagine that pivot point, and swing the whole thing around from there.

00:53

When we do that, our triangle ends up here…

00:55

…with point C at (-2, -1).

00:59

And now the easy part. When we reflect a shape across an axis, all we do is flip it.

01:04

We can see that point C now sits at (2, -1)…

01:07

…which is choice E, our final answer.

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