Ananth Narayan
I think there is no need of using trigonometry. It is very easy to cut at an angle 30 deg without even calculation.Hope you get it.
Yes, the slope is given as 30°, so no need for math.
Calculations are needed due to how the "depth" of the slot is given as 1.5 units along the sloped face.
This problem can be solved geometrically as Yahay did with the 3D sketch. Or match can be used to calculate the depth of cut in only the Z axis. Given the problem (√1.6875), a sketched solution is easier and not subject to rounding errors.
An alternative is sketching the slot profile on the sloped face and extruding along a vertical vector, but that's an extra feature in this low feature challenge.