Write the Product as a Sum or Difference of Trigonometric $\cos 36 ^ { \circ } \sin 21 ^ { \circ }$

question 84

Multiple Choice

Write the product as a sum or difference of trigonometric functions.
- $\cos 36 ^ { \circ } \sin 21 ^ { \circ }$

• A) \(\frac { 1 } { 2 } \left( \cos 57 ^ { \circ } + \cos 15 ^ { \circ } \right)\)
• B) \(\frac { 1 } { 2 } \left( \sin 57 ^ { \circ } - \sin 15 ^ { \circ } \right)\)
• C) \(\frac { 1 } { 2 } \left( \cos 57 ^ { \circ } - \cos 15 ^ { \circ } \right)\)
• D) \(\frac { 1 } { 2 } \left( \sin 57 ^ { \circ } + \sin 15 ^ { \circ } \right)\)

---

Definitions:

Thyroid Gland

An endocrine gland, consisting of irregularly spheroid follicles, lying in front and to the sides of the upper part of the trachea, in a horseshoe shape, with two lateral lobes connected by a narrow central portion, the isthmus; occasionally an elongated offshoot, the pyramidal lobe, passes upward from the isthmus in front of the trachea. It is supplied by branches from the external carotid and subclavian arteries, and its nerves are derived from the middle cervical and cervicothoracic ganglia of the sympathetic system. It secretes thyroid hormone and calcitonin.

Steroidal

Relating to or characterized by the presence of steroids, which are a large class of organic compounds with a characteristic molecular structure.

Cell Membrane

The outer limit of a cell that is thin and selectively permeable. It controls the movement of substances into and out of the cell.

Hormone

A chemical secreted by a cell that affects the functions of other cells.