1. The problem statement, all variables and given/known data particle experiencing SHM with frequency f= 10 hz find the displacement x at any time t for the following initial conditions. @ t=0 x=0.25m v=0.1 m/s 2. Relevant equations x=Asin(ωt+∅) v=Aωcos(ωt+∅) 3. The attempt at a solution So with frequency I find ω which then is subbed into the x=Asin(ωt+∅) @ t=0 to yield 0.25=Asin(∅). I then get v=Aωcos(ωt+∅) and sub in for v and t and ω and get 0.25=A(20∏)cos(∅) rearrange: 0.25/(20∏)=Acos(∅) I then divide these equations by each other and rearrange to get: arctan(50∏)= ∅ then with this I go back to 0.25=Asin(∅) and sub in ∅ rearrange to solve for A and its wrong! I get x=(0.16)sin(20∏t+1.56). answer in book says x=0.25cos(20∏t)+0.00159sin(20∏t). it says also acceptable solutions would be x=0.25sin(20∏t+1.56) and its cos variant. can someone please help I am confused about how they got this answer and how it is in that form.