Use an Addition or Subtraction Formula to Write $\cos 75 ^ { \circ } \cos 15 ^ { \circ } + \sin 75 ^ { \circ } \sin 15 ^ { \circ }$

question 77

Essay

Use an addition or subtraction formula to write $\cos 75 ^ { \circ } \cos 15 ^ { \circ } + \sin 75 ^ { \circ } \sin 15 ^ { \circ }$ and find its exact value.

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Definitions:

Heuristic

A problem-solving approach using practical methods or various shortcuts to produce solutions that may not be optimal but are sufficient for immediate goals.

Subgoal Activation

The process by which smaller objectives are targeted in order to achieve larger, overarching goals.

Functional Fixedness

The cognitive bias that limits a person to using an object only in the way it is traditionally used.

Stepwise Incrimination

A gradual increase in criminal behavior or severity of crimes committed, often observed in serial offenders.