David W. answered 08/07/15
Experienced Prof
Hi Bob,
This problem was written to give you practice using the x-y coordinate system to plot geometric objects and to understand how to read plots.
The Origin [ the point (0,0) ], the x-axis (positive x to the right) and the y-axis (positive y up) gives us the background orientation. [Note: Have you ever noticed in the very famous photo named “Earthrise” that Earth’s North is not UP?]
O.K., when a transposition is performed, the Origin is moved or else the object is moved in relationship to a fixed Origin.
This problem mentions, “Triangle … is translated 2 units right and one unit down.” This is poor wording, but I’ll assume that the object is moved in relationship to a fixed Origin.
That means that the new x values will be 2 units more than the old x values and the new values of y will be one unit less than the old values of y after triangle is moved. So, let’s write the new points under the old points so we can be super-accurate:
X(-1,-3) Y(-1,-1) Z(-3,-1)
+2 -1 +2 -1 +2 -1
X'(1,-4) Y'(1,-2) Z'(-1,-2)
One extra note: The points in this problem (X,Y,Z,X',Y',Z') are NOT THE SAME as the x and the y axis (and in 3-D Geometry, the Z-axis). It might have been less confusing to have named them A,B,C,A',B',C',