Which expression is equivalent to (sin x + 1)(sin x − 1)? a. cos2x b. -cos2x c. cos2x + 1 d. cos2x − 1 e. -cos2x + 1

ANSWER

B.

EXPLANATION

The given expression is

(sin x + 1)(sin x − 1)

Note that:

This implies that,

We can factor -1 on the right hand side to get,

Note that from the Pythagorean Identity

We apply this identity to obtain:

The correct choice is B

b

step-by-step explanation:

the equation of a line in point- slope form is

y - b = m(x - a)

where m is the slope and (a, b) a point on the line

calculate m using the slope formula

m = (y₂ - y₁ ) / (x₂ - x₁ )

with (x₁, y₁ ) = (0, 4) and (x₂, y₂ ) = (3, - 5) ← 2 points on the line

m = = = - 3

with m = - 3 and (a, b) = (3, - 5), then

y - (- 5) = - 3(x - 3), that is

y + 5 = - 3(x - 3) → b