??? It would be nice to know what "b" and "y" have to do with vector f!

So a, b, and y ( , , and ) are the direction angles, the angles vector f makes with the x, y, and z axes? It would have been nice if you had said that to begin with!i want to know if i did this equation right

i know that cosb = 2cosy

and i have the formula cos a^2 + cos b^2 + cos y^2=1

(I see now that you titled this thread "direction angles" but I still think you should have been more explicit.)

But youso i plug in cosb=2cosy in for cosb^2

and i get : cos45^2 + 2cosy^2 + cosy^2 = 1didn'tdo what you just said! If cos b= 2 cos y then .

No. (and be careful: Write either cos^2 y or (cos y)^2. "cosy^2" means cos(y^2).)then: .5+ 3cosy^2=1=

5 cos^2 y= .5 so cos^2 y= .1.3cosy^2= .5

y= 65.9 deg

then plug it back in to original

so: cos45^2+cosb^2+cos 65.9^2=1

then you get cosb^2=.333

cosb=sqrt(.333)

b=Cos^-1(.333)

b=54.74deg

thanks for the help