Projectile motion problem (find angle theta)

[5ymmetrica1]

Homework Statement

A projectile is launched from the ground with an initial velocity of 140m/s at an angle of θ above the horizontal. (assume AR is negligible and the ground is level)
The time of flight is 18.7seconds and its range is 1.98*10^3
show that the launch angle θ is approximately 41 degrees

Homework Equations

I'm unsure which equation I am supposed to use for a problem like this

The Attempt at a Solution

v_oh = 140cosθ

∴ cosθ = v_oh/140

but I am not given enough information to find the initial horizontal velocity so this equation won't work. I also am sure that I have to use the time of flight and the range since its been given but I can't think how to rearrange things to make it work.
Can anyone point me in the right direction for what I'm supposed to be doing please?

 

[rude man]

Homework Statement

A projectile is launched from the ground with an initial velocity of 140m/s at an angle of θ above the horizontal. (assume AR is negligible and the ground is level)
The time of flight is 18.7seconds and its range is 1.98*10^3
show that the launch angle θ is approximately 41 degrees

Homework Equations

I'm unsure which equation I am supposed to use for a problem like this

The Attempt at a Solution

v_oh = 140cosθ

∴ cosθ = v_oh/140

but I am not given enough information to find the initial horizontal velocity so this equation won't work. I also am sure that I have to use the time of flight and the range since its been given but I can't think how to rearrange things to make it work.
Can anyone point me in the right direction for what I'm supposed to be doing please?

What must v_oh be if the projectile flew for 1.98e3 m and took 18.7sec. to do so?

 

[5ymmetrica1]

thanks for the reply rudeman!

So v_oh = 1.8e3m/ 18.7s = 105.88 m/s

then θ = cos^-1 (105.88/140)

∴ θ = 40.86 degrees ≈ 41 degrees

 

[rude man]

thanks for the reply rudeman!

So v_oh = 1.8e3m/ 18.7s = 105.88 m/s

then θ = cos^-1 (105.88/140)

∴ θ = 40.86 degrees ≈ 41 degrees

Yay team!