Answer:
see explanation
Step-by-step explanation:
Using the trigonometric identity
sin²x + cos²x = 1 ⇒ sin²x = 1 - cos²x
Given
sin²x + 7cosx + 17
=1 - cos²x + 7cosx + 17
= - cos²x + 7cosx + 18 ← factor out - 1 from each term
= - (cos²x - 7cosx - 18)
Consider the factors of the constant term (- 18) which sum to give the coefficient of the cosx term (- 7)
The factors are - 9 and + 2, thus
= - (cosx - 9)(cosx + 2) ← in factored form
.00084 in scientific notation is 8.4 × 10^-4
