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

## Answer this Question

## Related Questions

- Trigonometry. - ( tanx/1-cotx )+ (cotx/1-tanx)= (1+secxcscx) Good one! ...
- Precalculus/Trig - I can't seem to prove these trig identities and would really ...
- Trigonometry - Prove the following trigonometric identities. please give a ...
- Precalculus/Trig - Prove the following identity: 1/tanx + tanx = 1/sinxcosx I ...
- Trig........ - I need to prove that the following is true. Thanks (cosx / 1-sinx...
- Trigonometry Check - Simplify #3: [cosx-sin(90-x)sinx]/[cosx-cos(180-x)tanx] = [...
- Trigonometry - Simplify #1: cscx(sin^2x+cos^2xtanx)/sinx+cosx = cscx((1)tanx)/...
- Math 12 - Simplify #1: cscx(sin^2x+cos^2xtanx)/sinx+cosx = cscx((1)tanx)/sinx+...
- trig - express this in sinx (1/ cscx + cotx )+ (1/cscx- cotx) i got 2sinx is ...
- Pre-Calc - Trigonometric Identities Prove: (tanx + secx -1)/(tanx - secx + 1)= ...