# what would be the first step in verifying the following identity? cos(x)*tan(x)=sin(x) Multiplication Substitution Evaluation This is not an identiy

### 3 Answers | Add Yours

You may select two options when solving the problem: either multiplication, or substitution, both options work perfectly.

Selecting the multiplication option, you will need to multiply both sides by 1/cos x such that:

(cos x*tan x)/cos x = sin x/cos x

Reducing like terms yields:

tan x = sin x/cos x

This last line represents the definition of tangent function, hence the given expression is an identity.

cos(x)*tan(x)=sin(x)

You could also use substitution:

tan(x) = sin(x)/cos(x)

cos(x) * sin(x)/cos(x) = sin(x)

The cosx cancels and you are left with

sin(x) = sin(x)

Since this is a true statement, we've probed that the premise is true.

cos(x)*tan(x)=sin(x)

**tan(x) = sin(x)/cos(x)**

replace in the original equation:

cos(x)*sin(x)/cos(x)=sin(x)

cos(x) simplifies with the denominator =>sin(x)=sin(x)

The answer is **Substitution**