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# matrix transformation, quick question Watch

1. I'm stuck on part b (question is attached)

I equated -sin x to 1/2 and got: x=30 and since it was a negative value it's in the 4th quadrant so a clockwise rotation of 30 degrees

but the mark scheme has the answer as anti-clockwise rotation of 210 or clockwise rotation of 150.

where am I going wrong?
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2. (Original post by Ravster)
I'm stuck on part b (question is attached)

I equated -sin x to 1/2 and got: x=30 and since it was a negative value it's in the 4th quadrant so a clockwise rotation of 30 degrees

but the mark scheme has the answer as anti-clockwise rotation of 210 or clockwise rotation of 150.

where am I going wrong?
sin is negative in the third and fourth quadrants.

Looking at your matrix, we also have cosine negative.

And the only quadrant where both sine and cosine are negative is the third quadrant, hence....

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