<p>Ok this was on my PLAN test. I missed it, and I can't figure out the correct answer.</p>
<p>There's a line with the equation y=2/3x + 6. If the line is rotated 90 degrees about the origin, what is the y intercept of the new line</p>
<p>When its rotated 90 degrees, the x-intercept of the original line becomes the y-intercept of the new line. The y-intercept is therefore (0, -9).</p>
<p>Yep, invert x & y and solve for y again.</p>
<p>thanks, i feel stupid now</p>
<p>The answer depends on how you rotate it.
If one follows convention and rotate it clockwise, the answer
is +9.
Then counterclockwise = -9.</p>
<p>No wonder SAT is so damn hard, retarded examiners.</p>
<p>the SAT isn't hard... and that wasn't an SAT problem</p>
<p>Following convention is rotating counterclockwise, not clockwise. But I do agree that this question is poorly written.</p>
<p>Your solution, as proposed earlier, is wrong.
Your numerical answer is correct, by accident.</p>
<p>Rotating any which way will not give the answer you posted earlier.</p>
<p>(x intercept does not become y intercept AND
y intercept does not become x intercept in the same
rotational transformation)</p>
<p>The matrix is
cos sin
-sin cos</p>
<p>The line is being rotated by 90 degrees
NOT the reference frame</p>
<p>I am done here.</p>
<p>I didn't state that it that changed for the general case, but for this case in particular only.<br>
If you do use the transformation matrix, you'd multiply
cos90 -sin90 = 0 1
sin90 cos90 -1 0
by
x
y</p>
<p>to get x' and y'. x'=-y and y'=x so that
-x'=2/3y'+6 and y'=-3/2x'-9, which is a y-intercept of -9. The matrix you provided is for a clockwise rotation; from my personal experience, whenever a question states a rotation, it usually means counterclockwise (for example, how do we usually measure angles?).</p>
<p>Crap....stuff didn't line up...</p>
<p>WOAH..that is so not an SAT question.</p>
<p>Damn. That was one of the few problems I ended up missing. I feel stupid.</p>
<p>Wow, matricies. Nice.</p>
<p>:)</p>
<p>No No No this was a PLAN question, you guys should get the correct answer w/o matricies or trig functions. I probably got the slope wrong (cant find sheet) but I believe the correct answer was 4. Oh amd it prolly said clockwise or counterclockwise I just don't remember which.</p>
<p>4? So no one got it?</p>
<p>well i think i wrote the question wrong, I can't find the sheets anymore</p>
<p>Using matrices was just the general way to solve the problem. It can be solved with just a little thought because the angle is nice.</p>