Answer:
sine A = four-fifths
Explanation:
You have a rectangle triangle ABC with hypotenuse AB 35, side CB 28 and side CA 21. The angle C is 90°.
In order to calculate sin A, you take into account that:
![sinA=(opposite\ side\ to\ A)/(hypotenuse)](https://img.qammunity.org/2021/formulas/mathematics/college/dqwdpyyln8dksaa6nsi8rtvvlll2kn1bna.png)
The opposite side to angle A is side CB = 28
Hypotenuse = 35
You replace the numeric values of the hypotenuse and side BC in the formula for sinA:
![sinA=(28)/(35)](https://img.qammunity.org/2021/formulas/mathematics/college/neg8b1ue4w9fkzdsvb4h86c1s7o2kzp2hv.png)
In order to simply the fraction, you divide both numerator and denominator by 7:
hence, the answer is
sine A = four-fifths