Wedensdays are makeups for holiday mondays. Sets - everything in graphics is just a set. Depends on def'n what it returns. Measure of two halves should be measure of whole thing, etc.
Integrals are always over some set wrt some measure.
Weighted avg preseves fact that average lies between extrema. Energies are always nonnegative, except in the Chemistry department. Solid angle - area of eclipsed region on the unit sphere. Both angle and solid angle are measures of sets. We will never use this.