Answer: [tex]59^{\circ}[/tex]
Step-by-step explanation:
Consider that ladder is making a right triangle with the burning building.
Let x be the angle of elevation of his ladder.
Then [tex]\Rightarrow\tan\ x=\frac{\text{height of building reached by ladder}}{\text{distance between ladder and building}}\\\\\Rightarrow\tan\ x=\frac{50}{30}=1.67\\\\\Rightarrow\ x=\tan^{-1}(1.67)\\\\\Rightarrow\ x=59.03^{\circ}\approx59^{\circ}[/tex]
Thus, the angle of elevation of his ladder is [tex]59^{\circ}[/tex]
