Answer:
∅ = 89.44° 
Explanation:
In situations like this air resistance are usually been neglected thereby making g= 9.81 m/
Bring out the given parameters from the question:
Initial Velocity ( ) = 1000 m/s
) = 1000 m/s 
Target distance (d) = 2000 m
Target height (h) =  800 m
Projection angle ∅ = ?
Horizontal distance =  tcos ∅     .......................... Equation 1
tcos ∅     .......................... Equation 1
where  = velocity in the X - direction
 = velocity in the X - direction
            t = Time taken
Vertical Distance = y =  t -
 t -  g
g ................... Equation 2
        ................... Equation 2
Where    = Velocity in the Y- direction
 = Velocity in the Y- direction
               t  = Time taken 
 =
 =  sin∅
sin∅
Making time (t) subject of the formula in Equation 1
                     t = d/( cos ∅)
cos ∅)
                       t =  =
 =  =
  =     ...................Equation 3
             ...................Equation 3
substituting equation 3 into equation 2
Vertical Distance = d =  
  -
  -  g
g
                                   Vertical Distance = h =  sin∅  -
  -  g
g
   Vertical Distance = h = dtan∅   -  g
g
   Applying geometry 
                                =
 =  + 1
 + 1
   Vertical Distance = h = d tan∅   - 2 g ( + 1)
 + 1)
                substituting the given parameters
                800 = 2000 tan ∅ - 2 (9.81)(  + 1)
 + 1)
               800 = 2000 tan ∅ - 19.6(  + 1)  Equation 4
 + 1)  Equation 4
Replacing tan ∅ = Q     .....................Equation 5
In order to get a quadratic equation that can be easily solve.
             800 = 2000 Q - 19.6 + 19.6
 + 19.6
Rearranging 19.6 - 2000 Q + 780.4 = 0
 - 2000 Q + 780.4 = 0
                      = 101.6291
 = 101.6291
                        = 0.411
 = 0.411
     Inserting the value of Q Into Equation 5
                  tan ∅ = 101.63    or tan ∅ = 0.4114 
Taking the Tan inverse of each value of Q 
                   ∅ = 89.44°     ∅ = 22.37°