To rotate a point \((x, y)\) clockwise about the origin by 90 degrees, you can use the following transformation:
\[ (x, y) \rightarrow (y, -x) \]
For the point \((1, 2)\):
- \(x = 1\)
- \(y = 2\)
Applying the transformation gives:
\[ (1, 2) \rightarrow (2, -1) \]
Thus, the new point after rotating \((1, 2)\) 90 degrees clockwise about the origin is \((2, -1)\).