Sunday

November 23, 2014

November 23, 2014

Posted by **.** on Tuesday, April 20, 2010 at 4:03pm.

sin2x/cosx + sinx = 2sinx

Solve for all values of x:

6cos2x-7cosx-3=0

If f(x)=cos1/2x-sin2x find the value of

f(pi)

- Trigonometry -
**Reiny**, Tuesday, April 20, 2010 at 5:33pmthe first identity is not correct

LS = sin2x/cosx + sinx

= 2sinxcosx/cosx + sinx

= 2sinx + sinx

= 3 sinx

You have RS = 2sinx

6cos2x-7cosx-3=0

You probably typed this incorrectly and really meant

6cos^2 x-7cosx-3=0

if so, let cosx = y, then our equation becomes

6y^2 - 7y - 3 = 0

(2y - 3)(3y + 1) = 0

y = 2/3 or y = -1/3

cosx = 2/3 or cosx = -1/3

for cosx = 2/3, x is in I or IV

x = 48.2 or 311.8°

for cosx = -1/3, x is in II or III

x = 109.5 or 250.5°

for the last one, sub in x = π

**Answer this Question**

**Related Questions**

Trig - Verify the identity: tanx(cos2x) = sin2x - tanx Left Side = (sinx/cosx)(...

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

math - solve each equation for 0=/<x=/<2pi sin^2x + 5sinx + 6 = 0? how do ...

maths - by equating the coefficients of sin x and cos x , or otherwise, find ...

Math - prove identity Sin2x - sinx/cosx + cos2x= sinx/cosx + 1

Math please help quick - Which of the following are identities? Check all that ...

check math - Here are my answers. Can you check if I got the right answers? ...

Trig - If secx = 8 and -pi/2 < x < 0, find the exact value of sin2x Use ...

Trigonometry - Simplify #1: cscx(sin^2x+cos^2xtanx)/sinx+cosx = cscx((1)tanx)/...

Trigonometry - Find all values of x such that sinx+sin2x=0 and 0 <= x <= ...