Wednesday

March 4, 2015

March 4, 2015

Posted by **cheyanne** on Friday, February 24, 2012 at 1:20am.

tan (-15 degrees)

2) Rewrite the following expression as a trigonometric function of a single angle measure.

cos 3x cos 4x - sin 3x sine 4x

- TRIG/ALGEBRA -
**Reiny**, Friday, February 24, 2012 at 8:42am1.

tan 15 = tan(45-30)

= (tan45-tan30)/(1 + tan45tan30)

= (1 - 1/√3)/(1 + 1/√3)

multiply by √3/√3

= (√3-1)/(√3+1)

but tan(-15) = -tan15

so

tan(-15°) = (1-√3)/(√3 + 1)

cos 3x cos 4x - sin 3x sine 4x

= cos(3x+4x) = cos 7x

**Answer this Question**

**Related Questions**

Trigonometry - use the appropriate trig identity (sum and difference, half angle...

Mathmatics - a. Use the formulas for lowering powers to rewrite the expression ...

trig - use sum or difference identities to find the exact value of the ...

Math- Trig - 1. Determine the exact value of cos^-1 (pi/2). Give number and ...

Please help Math - a. Use the formulas for lowering powers to rewrite the ...

MATH - 1.)Find the exact solution algebriacally, if possible: (PLEASE SHOW ALL ...

trig - use a sum or difference identity to find an exact value cos pie/12

trig help much appreciated! :)) - 1. Find the complete exact solution of sin x...

trig - use a half-angle identity to find the exact value of tan 105 degrees.

trig - Use a sum or difference identity to find the exact value. tan 25deg + ...