Use a half-angle identity to find the exact value of cos 15º.

Step-by-step explanation:

so the angle we will use in our identity is 30 degrees. The formula is

which simplifies to

which simplifies to

which simplifies to

which simplifies, finally, to

, choice a.

b. y = 4x - 2

step-by-step explanation:

to find a parallel equation to an equation, make sure both equations have the same slope but different y-intercepts.

y = 4x + 1

4 = slope

1 = y-intercept

y = 4x - 2

4 = slope

-2 = y-intercept

they both have the same slope but different y-intercepts, so, b. is the correct answer.

and to check your work, you can graph both equations. : )