Saturday
May 25, 2013

# Homework Help: Math

Posted by Rivan on Saturday, April 21, 2012 at 2:08am.

6cos^2 theta + 5cos theta=1
Solve for theta

• Math - Bosnian, Saturday, April 21, 2012 at 4:02am

Substitute :

cos ( theta ) = u

6 cos ^ 2 ( theta ) + 5 cos ( theta ) = 1

6 u ^ 2 + 5 u = 1

6 u ^ 2 + 5 u - 1 = 0

The exact solutions are :

u = 1 / 6

cos ( theta ) = 1 / 6

theta = cos ^ - 1 ( 1 / 6 )

_________________________________

cos ^ - 1

is the inverse cosine function

__________________________________

and

u = - 1

cos ( theta ) = - 1

theta = pi [ radians ] = 180 °

The cosine function have periode 2 pi n

where nis an integer.

So the solutions are :

theta = 2 pi n + cos ^ - 1 ( 1 / 6 )

theta = 2 pi n - cos ^ - 1 ( 1 / 6 )

and

theta = 2 pi n + pi

theta = 2 pi n - pi

P.S.

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6 u ^ 2 + 5 u - 1 = 0

When you see list of results click on:

When page be open in rectangle type:

6 u ^ 2 + 5 u - 1 = 0

and click option: solve it

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