need help to fix the angle

[sonicflare9]

Over a completely flat surface a ball weighing 0.8kg is thrown with a speed of 50m/s
what angle must it be thrown at to land 100m away

[Baltuilhe]

Good night!

Use the following:
[tex]\sin(2\theta)=\frac{d\cdot g}{v^2}[/tex]
Where:
d=100m
g=9,81m/s^2
v=50m/s

So:
[tex]\sin(2\theta)=\frac{100\cdot 9,81}{50^2}=0,3924[/tex]
[tex]2\theta\approx 23,1039^{\circ}\Rightarrow\theta\approx 11,5520^{\circ}[/tex]
[tex]2\theta\approx 156,8961^{\circ}\Rightarrow\theta\approx 78,4480^{\circ}[/tex]

Hope to have helped!