Posted by **LiNnda** on Thursday, May 6, 2010 at 8:02am.

1) ctgx+cosx=1+ctgx*cosx

2) sin^4x+cos^4x=1/2

3) (sinx-cosx)^2=sin2x

4) sin^4x-cos^4x=7/2(sinxcosx)

5) sin^2x-sinxcosx+cosx-sinx=0

- Not doing all those, already know how -
**Damon**, Thursday, May 6, 2010 at 8:18am
How about you try first and post your results.

- equations trig -
**LiNnda**, Thursday, May 6, 2010 at 8:51am
2) sin^4x+cos^4x=1/2

sin^2x*sin^2x+cos^4x=1/2

(1-cos^2x)(1-cos^2x)+cos^4x=1/2

1-cos^2x-cos^2x+2cos^4x=1/2

2cos^4x-2cos^2x+1=1/2

2cos^4x-2cos^2x+1/2=0

x=pi/4+2kpi x2=7pi/4+2kpi

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