Posted by **just** on Tuesday, March 27, 2007 at 9:36pm.

Prove: (3cosx + 4sinx)^2 + (4cosx - 3sinx)^2=5 ...this is all under the square root sign.

this is what i did please check.

i multipied both binomials. but i get cos square x..and sincosx ..how do i combine them..please help!

In this case, after multiplying binomials, there will be 24sincos and -24sincos terms that cancel. That will leave you with sin^2 and cos^2 terms. Write sin^2 as 1-cos^2 and solve for cosx

i get 9cos^2x + 16sin^2x +16cos^2x + 9sin^2x

now i know that sin^2 equals 1-cos^2....so would that be 9cos^2x + 17-cos^2x+16cos^2+ 10cos^2x? if not please help..and if this is correct..what would come after this step?

## Answer This Question

## Related Questions

- precal! - Prove: (3cosx + 4sinx)^2 + (4cosx - 3sinx)^2=5 ...this is all under ...
- Math radical equations - Please show me how to do these step by step because I ...
- Math simplifying mixed radicals - Please help me simplify these following mixed ...
- Math simplifying mixed radicals - Please help me simplify these following mixed...
- Algebra - Rationalize each expression by building perfect nth root factors for ...
- math - Here's my question: Determine if each system has one, two, or no ...
- Algebra-Please help-I'm desperate to understand - Posted by Megan on Tuesday, ...
- Math - Combine like terms. 7a square root 2 - a square root 2 + 16= My answer ...
- Math/Algebra HELP - Can you please check these answers: 1. If the first Now= -9...
- Algebra 1B - I really need help with this but I'm not sure if I'm going to put ...

More Related Questions