1. The problem statement, all variables and given/known data A kaon (denoted K0) is an unstable particle of mass 8.87 × 10−28kg. One of the means by which it decays is by spontaneous creation of two pions, a π+and a π−. Both the pions have a mass of 2.49 × 10−28kg. Suppose that a kaon moving in the +x direction decays by this process with the π+ moving oﬀ at speed 0.9c and the π−at 0.8c. (a) What was the speed of the the kaon before decay? (b) In what directions do the pions move after the decay? mass of kaon = 8.87x10^28 kg mass of both pions = 2.49x10^-28 kg u of pion+ = 0.9c u of pion- = 0.8c I solved part a) and found that the speed of the kaon before decaying was approximately 0.437c and just need a little help with the second part 2. Relevant equations momentum in x direction = γkmkuk= γ+m+u+ + γ-m-u- momentum in y direction = 0 = γ+m+u+ - γ-m-u- where the + and - subscripts are for the + pion and - pion and k is for the kaon 3. The attempt at a solution so basically i plugged in what I knew, and reduced everything to this: Momentum in x direction = 4.30 = 5.13cosθ+ + 3.33cosθ- Momentum in the y direction = 3.33sinθ-= 5.13sinθ+ i have 2 thetas and I'm not really sure how to go about finding the angles... I cancelled the c's and the x10^-28 from both sides to make it a little bit nicer but I'm just stuck... here any advice would be great :) PS: for my past life, i seen people dividing equations by each other a lot cancel things out. If anyone can also provide an explanation to what is really happening, it would be nice too.