Tuesday

October 21, 2014

October 21, 2014

Posted by **Josh** on Monday, October 10, 2011 at 9:32am.

6(cosx)^2-cosx-5=0 on (pie/2, pie)

- Calculus -
**bobpursley**, Monday, October 10, 2011 at 9:37amIsn't this a quadratic in cosx ?

6y^2-y-5=0

y=(1+-sqrt(1+120))/12

where y= cos x

then solve for x

- Calculus -
**Reiny**, Monday, October 10, 2011 at 9:43amby formula

cosx = (2 ± √124)/12

= -.76129 or 1.09.. , the latter is undefined

x = 2.436 radians

or x = cos^-1 ( (2-√124)/12)

- bobpursley is right - Calculus -
**Reiny**, Monday, October 10, 2011 at 9:47amI misread your equation, should be

x = cos^-1 ( 1 ± √121)/12)

= cos^-1 (-5/6)

**Answer this Question**

**Related Questions**

Maths - Could someone help me with this question Write in polar form : sinx - i ...

Math - What is the derivative of ((e^pie/3)(cosx))? Is it pie/3e^pie/3 times ...

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

Maths - Solve this equation fo rx in the interval 0<=x<=360 3sinxtanx=8 I ...

Math - How many solutions does the equation cosx + 1/2 = 1 have for 0<x<...

Calculus grade 12 - solve for (<_ = less than or equal to / pie = pie sign...

advanced functions grd 12 - im not sure wheer to start and how to do solve this ...

calculus - Can someone explain how find the average rate change for these ...

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

physics - The motion of a particle is described by x = 10 sin (piet +pie/2 ). At...