Answer:
76°
Step-by-step explanation:
In projectile, 
Maximum height = 
 and range =
 and range = 

u = velocity of the body
 = angle of launch
 = angle of launch
g = acceleration due to gravity
If the range equals the maximum height in an ideal projectile launch on a horizontal plane, this means;
 

since 


The angle at which the range equals the maximum height in an ideal projectile launch on a horizontal plane is approximately 76°