A ramp is 4 m long along its slope and rises 1.4 m…

Step 1. The sine. $\sin\theta = \dfrac{1.4}{4} = 0.35$.

Step 2. The angle. The principal value is $\theta = \sin^{-1}0.35 = 0.3576$ radians. In degrees this is $0.3576 \times \dfrac{180}{\pi} = 20.49^\circ$.

Step 3. The other angle. Since $\sin(180^\circ - \theta) = \sin\theta$, the other angle is $180^\circ - 20.49^\circ = 159.51^\circ$.

Step 4. Why not. An angle of $159.51^\circ$ is obtuse. A ramp that rises from the ground makes an acute angle, so only $20.49^\circ$ is possible.