Verify the identity cosx cos(-x) - sinx sin(-x) =1

(identity has been verified)

Step-by-step explanation:

Verify the following identity:

cos(x) cos(-x) - sin(x) sin(-x) = 1

Hint: | Cosine is an even function.

Use the identity cos(-x) = cos(x):

cos(x) cos(x) - sin(-x) sin(x) = ^?1

Hint: | Sine is an odd function.

Use the identity sin(-x) = -sin(x):

cos(x) cos(x) - -sin(x) sin(x) = ^?1

Hint: | Evaluate cos(x) cos(x).

cos(x) cos(x) = cos(x)^2:

cos(x)^2 - ( - sin(x) sin(x)) = ^?1

Hint: | Evaluate -(-sin(x)) sin(x).

-(-sin(x)) sin(x) = sin(x)^2:

cos(x)^2 + sin(x)^2 = ^?1

Hint: | Use the Pythagorean identity on cos(x)^2 + sin(x)^2.

Substitute cos(x)^2 + sin(x)^2 = 1:

1 = ^?1

Hint: | Come to a conclusion.

The left hand side and right hand side are identical:

(identity has been verified)

x= cost per bracelet

number of bracelets * x + shipping charge = total cost

so

9x+9=72

step-by-step explanation:

infinity is the answer