Write the following expression as a function of a positive acute angle. Use "+" to indicate a positive value and "-" to indicate a negative value.

Sin312° = ?

Answer: sin (312°) = - sin (48°)

Justification:

1) 312° ⇒ 270° < 312° < 360° ⇒ third quadrant ⇒ sign of sin (312°) is negative

2) Acute angle:

angle = 360° - 312° = 48°

⇒ sin (312°) = - sin (48°) ← this is the expression requested.

Using the calculator you can find the value sin (312°) = - sin (48°) ≈ - 0.743