Someone please help me! Studying for finals and don’t understand how to complete problems like this! Thank you!

(d).

Step-by-step explanation:

sin² β + cos² β = 1

cos (α + β) = cos α cos β - sin α sin β

cos α = √(1 - ) = 21 / 29

cos β = 12 / 13

sin β = √(1 - ) = 5 / 13

sin α = 20 / 29

cos (α + β) = × - × =

step-by-step explanation:

to determine whether a given function is even, we simply substitute x with -x in the expression. if the result after simplification is identical to the original equation, then the function is said to be even other wise odd.

f(-x) = (-x)^2 - (-x) + 8

      = x^2 + x +8

the resulting function is not identical to the original one;

f(-x) ≠ f(x)

therefore, f(x) is not an even function