Saturday

December 20, 2014

December 20, 2014

Posted by **Sara** on Saturday, June 19, 2010 at 1:06pm.

2sinxcosx + cosx =0

2sinxcosx = -cosx

2sinx = -cosx/cosx

sinx = -1/2

{210, 330)

Is this correct?

- trig -
**Reiny**, Saturday, June 19, 2010 at 5:41pmno , you only have half the answers

2sinxcosx + cosx =0

cosx(2sinx + 1) = 0

cosx = 0 or sinx = -1/2

if cosx = 0, x = 90° , 270°

if sinx = -1/2, x = 210°, 330°

(you only had the last case)

**Answer this Question**

**Related Questions**

Trig (Last URGENT) - sin2x+cosx=0 , [-180,180) = 2sinxcosx+cosx=0 = cosx(2sinx+1...

Trig....... - I need to prove that the following is true. Thanks (2tanx /1-tan^x...

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] = [...

Pre-Calc - Trigonometric Identities Prove: (tanx + secx -1)/(tanx - secx + 1)= ...

Math - Verify the identity . (cscX-cotX)^2=1-cosX/1+cosX _______ sorry i cant ...

maths - hey, i would really appreciate some help solving for x when: sin2x=cosx ...

Precalculus/Trig - I can't seem to prove these trig identities and would really ...

mathh - this is for proving identies and its fustrating i can't solve this one ...

Precalculus/Trig - Prove the following identity: 1/tanx + tanx = 1/sinxcosx I ...