Finding exact value using half angle identities
Why is my answer incorrect?

Step-by-step explanation:

Your mistake is here: cos(-45°) = +½√2, not -½√2.

±√((1 + ½√2) / 2)

= ±√((2 + √2) / 4)

Option b = 90 degrees of freedom.

Step-by-step explanation:

So, in this particular Question we are given the following parameters or data or information which is going allow us to be able to solve this particular problem or Question;

=> "A regression analysis involved 8 independent variables"

=> "99 observations. "

Requirement : to determine the critical value of t for testing the significance of each of the independent variable's coefficient.

Hence, the formula below will used in Calculating or in the determination of the degree of freedom;

Degree of freedom= total number of observations - number of independent variables- 1.

Thus, slotting bin the values into the formula above, we have;

The degree of freedom = 99 - 8 - 1 = 90.