Thursday

March 5, 2015

March 5, 2015

Posted by **Anonymous** on Wednesday, February 22, 2012 at 11:11pm.

= 2sinxcosx+cosx=0

= cosx(2sinx+1)=0

cosx=0

x1=cos^-1(0)

x1=90

x2=360-90

x2=270

270 doesn't fit in [-180,180) what do I do? Or maybe I did something wrong.

sinx=1/2

x1=sin^-1(1/2)

x1=30

x2=180-30

x2=150

is this correct?

Please and Thank you

- Trig (Last URGENT) -
**Reiny**, Wednesday, February 22, 2012 at 11:18pmbut your domain is from -180 to 180 , so even though 270 will work in the equation , it is beyond your domain.

But, by looking at the cosine graph , you will see that it also has an x-intercept at x = -90°

so for your first one,

x = -90, 0, 90

the second part for sinx = 1/2

your answers of 30° or 150° are correct for the given domain.

**Answer this Question**

**Related Questions**

trig - Solve for [0, 360) 2sinxcosx + cosx =0 2sinxcosx = -cosx 2sinx = -cosx/...

Trigonometry Check - Simplify #3: [cosx-sin(90-x)sinx]/[cosx-cos(180-x)tanx] = [...

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

pre-calc - Solve: cos(2x-180) - sin(x-90)=0 my work: cos2xcos180 + sin2xsin180= ...

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+...

math - tanx+secx=2cosx (sinx/cosx)+ (1/cosx)=2cosx (sinx+1)/cosx =2cosx ...

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

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

math b - if sinx=(4/5), where 0 degrees<x<90 degrees, find the value of ...