Posted by **Rony** on Saturday, March 27, 2010 at 1:06pm.

the expression cos4x cos3x + sin4x sin3x is equivalent to

which one of the following is the answer:

1) sinx

2) sin7x

3) cosx

4) cos7x

- math(advanced algebra&trigonometry) -
**drwls**, Saturday, March 27, 2010 at 3:33pm
Look up the equation for cos(x-y) and it should be obvious what the answer is.

Think of x as 4x and y as 3x.

http://www.csgnetwork.com/trigtriformulatables.html

- math(advanced algebra&trigonometry) -
**Rony**, Sunday, March 28, 2010 at 11:47am
it is cosx

thanks

- math(advanced algebra&trigonometry) -
**Dewesh kumar**, Monday, October 4, 2010 at 12:17am
Seca=4x + 1/x than secb + tana what please tell me after 2days

## Answer This Question

## Related Questions

- Algebra/trigonometry - The expression cos4x cos3x+ sin4x sin3x is equilvalent to...
- Trigonometry - Simplify the expression using trig identities: 1. (sin4x - cos4x...
- trig - find all values of x on interval 0-2pi. (sin4x)(cos7x)=(cos4x)(sin7x) ...
- Trig - Simplify: (cosx + cos2x + cos3x + cos4x + cos5x + cos6x) / (sinx + sin2x...
- Trig - cos4x*cos3x + sin4x*sin3x
- trigonometry - Prove: sin3x-sinx/cos3x-cosx=-cot2
- Trig - Prove the following functions: (sinx+sin2x)/(1+cosx+cos2x)=tan x (cos3x/...
- Trigonometry - Can you please help me verify these? >sin7x-sin5x= tanx(cos7x-...
- trigonometry - can i use factoring to simplify this trig identity? the problem ...
- Trigonometry Check - Simplify #3: [cosx-sin(90-x)sinx]/[cosx-cos(180-x)tanx] = [...

More Related Questions