Question 1115048
a*cos(x) + b*sin(x) = c * sin(x + p)

c = {{{ sqrt(a^2+b^2) }}}
p = phase shift = {{{ tan^-1(a/b) }}} 

You have
  a=6
  b=8
  (and x=10t which just gets carried along)

so you can plug in to find

{{{ highlight(V =  V[1] + V[2] = 10sin(10t + 36.8699^o) ) }}}

——
To get the phase shift in radians:  {{{ 36.8699 * ( pi/180 )  = 0.6435 }}} radians