Final answer:
The given data lacks context for determining the missing angles a, b, and c. For d, approximations are made but they don't seem to answer the question about missing angles without further context.
Step-by-step explanation:
The student has asked to find the missing angles. The details provided do not sufficiently determine the missing angles for situations (a) 135°, (b) 143°, and (c) 125°, as the context or relationship of these angles is not defined. However, for situation (d), which seems to involve calculations related to angular displacement or angular velocity, the provided work approximates a second angle, θ20₁, as 29° which is approximately twice 15.56°, leading to an approximate value of 31.1°. This does not seem to directly answer the student's question about missing angles, but it does relate to angles. Without additional context or relationship between the angles, a complete and accurate answer cannot be provided.