\(\displaystyle{x}={v}_{{0}}{t}{\cos{\alpha}}\)

\(\displaystyle{y}={v}_{{0}}{\sin{\alpha}}{t}+{\frac{{{1}}}{{{2}}}}{>}^{{2}}\)

Final velocity v=0

\(\displaystyle{v}^{{2}}-{{v}_{{0}}^{{2}}}={2}{g}{h}\)

Where x=1.8m,y=-1.4m,v=0, \(\displaystyle{g}={9.81}\frac{{m}}{{s}^{{2}}}\)

This values are sustitute in equations (1),(2)&(3)

Then solve find \(\displaystyle{v}_{{0}},\alpha\)

\(\displaystyle{y}={v}_{{0}}{\sin{\alpha}}{t}+{\frac{{{1}}}{{{2}}}}{>}^{{2}}\)

Final velocity v=0

\(\displaystyle{v}^{{2}}-{{v}_{{0}}^{{2}}}={2}{g}{h}\)

Where x=1.8m,y=-1.4m,v=0, \(\displaystyle{g}={9.81}\frac{{m}}{{s}^{{2}}}\)

This values are sustitute in equations (1),(2)&(3)

Then solve find \(\displaystyle{v}_{{0}},\alpha\)