Co-Function Identities for Calc AB?

Test Preparation AP Test Preparation
1

<p>Are the co-function identities needed on the Calc AB exam?</p>

<p>sin (pi/2 - u) = cos u</p>

<p>etc. </p>

<p>Thanks, guys.</p>

2

<p>I don’t believe so.</p>

3

<p>Thanks, TheMathProf. I was hoping I would get a response from you. :)</p>

<p>I was doing a practice problem from that CB pdf document and the first question </p>

<p>lim [cos (3pi/2 + h) - cos (3pi/2)]/h
h->o</p>

<p>requires one of the sum-difference formulas. I thought that if they are going to use something that obscure, then they might as well use some of the co-function identities.</p>

4

<p>Actually, you don’t need the cofunction identities for that piece. What they’ve given you is the definition of the derivative for the function f(x) = cos (x) evaluated at x = 3pi/2. The derivative of cos(x) is -sin(x), and -sin(3pi/2) = 1.</p>

5

<p>Ah, great point! Thanks! </p>

<p>I really should have recognized the definition of the derivative, but it has been 4 months since I last took calculus. I just picked up the PR book to start reviewing for the AP exam. :)</p>