# Sum and Difference Formulas

• Jun 9th 2008, 06:27 PM
gabrie30
Sum and Difference Formulas
For Sin and Cos are easy but what about Sec?

Ex) Sec(-pi/12)

what would the sum and difference formula look like?
• Jun 9th 2008, 06:30 PM
mr fantastic
Quote:

Originally Posted by gabrie30
For Sin and Cos are easy but what about Sec?

Ex) Sec(-pi/12)

what would the sum and difference formula look like?

$\frac{1}{\cos \left( \frac{\pi}{4} - \frac{\pi}{3} \right)}$.
• Jun 9th 2008, 06:42 PM
gabrie30
Quote:

Originally Posted by mr fantastic
$\frac{1}{\cos \left( \frac{\pi}{4} - \frac{\pi}{3} \right)}$.

Right, but what if you had to find the exact value? What would the formula look like?
• Jun 9th 2008, 06:49 PM
Jonboy
you need to simplify the bottom of the fraction that mr fantastic gave you.

go here: Table of Trigonometric Identities

Look under "Sum-Difference Formulas"

Then pick the second one that involves Cos.