In a right-angled triangle ABC (angle C = 90), AB = 10 cm. Find BC if angle A = 25 degrees.

In this triangle, AB is the hypotenuse.
So we know that:
AB = 10 cm;
CB = 5 cm;
∠ А = 30 °.
Then we can calculate ∠B.
∠ В = 90 ° – 30 °;
∠ B = 60 °.
Consider Δ СВН – rectangular.
Since ∠ В = 60 °, then we can find ∠ ВСН.
∠ ВСН = 90 – 60;
∠СВН = 30 °.
Find ∠ AСН:
∠ AСН = 90 ° – 30 °;
∠ AСН = 60 °.
Answer: 30 °, 60 °.