would like to solve the equation for theta:

z = b*cos(theta) + a*cos(theta)

been a long time since i took trig, any help would be appreciated.

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- Apr 14th 2013, 03:52 PMbmorestudenthelp w/ trig equation
would like to solve the equation for theta:

z = b*cos(theta) + a*cos(theta)

been a long time since i took trig, any help would be appreciated. - Apr 14th 2013, 05:12 PMtopsquarkRe: help w/ trig equation
- Apr 14th 2013, 06:09 PMHallsofIvyRe: help w/ trig equation
Are you sure you didn't mean ? That's a much more interesting question. As topsquark says, your equation is just a matter of combining those two " terms.

To solve , use the identity sin(A+B)= sin(A) cos(B)+ cos(A) sin(B). That would be the same as the previous equation if a= sin(A) and b= cos(A). The problem with that is that we would have to have which is not, in general, true. We can fix that factoring out. That is, we write the equation as

so that

So that now

Now, we**can**let and so that the equation can be written

then

- Apr 14th 2013, 09:26 PMbmorestudentRe: help w/ trig equation
thanks for the quick replies! yes, i meant to type b*SIN(theta), not cos. glad you caught that mistake and answered it hallsofivy, many thanks!