# :trigonometric identity question

1. Jan 12, 2010

### Edgar92

URGENT:trigonometric identity question

1. The problem statement, all variables and given/known data
tan2x+cos2x+sin2x=sec2x
*the 2 stands for squared since I dont know how to make the squared symbol appear on a compter

2. Relevant equations
http://www.analyzemath.com/Trigonometry_2/Trigonometric_identities.html
stuff from this website and more

3. The attempt at a solution
(sin2x+cos2x(cos2x)+sin2xcos2x)/cos2x

1+cos2x+sin2xcos2x/cos2x

1+sin2xcos2x

any help is appreciated as I have been at this for over an hour and cant figure it out and it needs to be done soon

2. Jan 12, 2010

### rock.freak667

3. Jan 12, 2010

### icystrike

Re: URGENT:trigonometric identity question

take note of this identities:
tan²x=sec²x-1
cos²x+sin²x=1

4. Jan 12, 2010

### Fightfish

Re: URGENT:trigonometric identity question

Or you can work from "base principles" replacing sin x with opposite over hypotenuse, cos x with adjacent over hypotenuse et cetera

5. Jan 12, 2010

### Staff: Mentor

Re: URGENT:trigonometric identity question

A better idea would be to replace tan2(x) with (sin2(x))/(cos2(x)) and sec2(x) with 1/(cos2(x)). That way all your quantities would be in terms of powers of sinx and cosx.