In triangle abc, the angle c is 90, ab = 25, ac = 15. Find sinA.

To begin with, draw a triangle ABC with a right angle C and note in the figure that AB = 25 and AC = 15.
then we write “Find: sinA -?”
Decision:
sinA = CB / AB
Since AB we know, then we need to find SV. This can be done using the Pythagorean theorem (subtract the leg squared from the hypotenuse squared).
BUT! We can notice that we have Pythagorean numbers: 25 (5 * 5), 15 (3 * 5) and the missing leg 20 (4 * 5).
We can now find the sine. sinA = 20/25 = 0.8
Answer: 0.8