1. The problem statement, all variables and given/known data Two space ships are approaching each other a)if the speed of each is .9 *c relative to Earth , what is the speed of one relative to the other b)if the speed each relative to Earth is 30000m/s, what is the speed of one relative to the other 2. Relevant equations The problem does not state if the two rockets are headed toward each other on the x-axis , y-axis or z-axis , so I'm not really sure what velocity equations I should used and so I will list them all. u'(z)= u(z)/(gamma*(1-(v*u(z))/c^2) u'(y)= u(y)/(gamma*(1-(v*u(x))/c^2) u'(x)=u(x)-v/(1-v*u(x)/c^2) / 3. The attempt at a solution Here is my attempted solution for the first part part of the problem: a) u'(z)=u(z)-.9c/(2.29*((1)- u(z)*(.9c)/c^2)) u'(y)= u(y)/(2.29*((1)-u(y)*(.9c)/c^2)) u'(x)=u(x)-.9c/(1-.9c*u(x)/c^2) not sure how to calculate u(z),u(x), or u(y).