Two angles are said to be complementary, if the sum of the two angles is 90 degrees.
Given that the measure of angle SWT is 50 degrees, thus, the measure of the complementary angles will be 90 - 50 = 40 degrees.
From the diagram, the measure of angle USP is 40 degrees, hence it is a complement of angle SWT.
Recall that the angle on a straight line is equal to 180 degrees, thus the sum of the measures of angles USP, WST and TSV is 180 degrees.
i.e. mUSP + mWST + mTSV = 180 degrees
40 + 100 + mTSV = 180
mTSV = 180 - 140 = 40 degrees.
Hence angle TSV is complementary to angle SWT.
Therefore, the complementary angles to angle SWT are angle USP and angle TSV.
