In a triangle ABC right angled at B, AB = 5 cm and AC = 10 cm. Determine ∠ BCA.

Given, ΔABC is right angled at B
Where, AB = 5 cm and AC = 10 cm

AB is the opposite side and AC is the hypotenuse to the given triangle.
∴ Let's use sin ∠BCA = $\frac{\text{AB}}{\text{AC}}$= $\frac{\text{5}}{\text{10}}$=$\frac{\text{1}}{\text{2}}$

As we know sin 30° = $\frac{1}{2}$

So, sin ∠BCA = sin 30° or ∠ BCA = 30°
∴ ∠BCA = 30° is our answer.