Which of the following is not equivalent to cos pi over 5 1. cos negative pi over 5 2. cos 9pi over 5 3. cos 4 pi over 5 4. cos 11 pi over 5

The expression that is not equivalent to is:

                   3.  

We are asked to find which of the expression is not equivalent to:

1)

We know that:

Hence, we get:

Hence, option: 1 is incorrect.

2)

We know that:

As we know that:

Hence, we have:

Hence, option: 2 is incorrect.

4)

We know that:

As we know that:

Hence, we have:

Hence, option: 4 is incorrect.    

3)

We know that:

As we know that:

Hence, we have:

                Hence, option: 3 is the answer.

35 is an outlier

step-by-step explanation: