Answer: Option B.
Explanation:
You neeed to use the trigonometric identity:
![sin\alpha=(opposite)/(hypotenuse)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6j5eh56eb8lcstqvo7zl1n0flvsxdmjmip.png)
As you need to find sin∠A, you can identify in the right triangle that:
![opposite=8\\hypotenuse=10\\\alpha=A](https://img.qammunity.org/2020/formulas/mathematics/college/me1iqbrb3zqhyf0l9rkl3kkvq3x6k2t0t1.png)
Finally, substitute the angle, the lenght of the opposite side and the lenght of the hypotenuse into
to find sin∠A. Then, you get:
![sinA=(8)/(10)](https://img.qammunity.org/2020/formulas/mathematics/college/r151en67c8v2b05vusap1zgljaxm8xm2ow.png)
Reducing the fraction:
![sinA=(4)/(5)](https://img.qammunity.org/2020/formulas/mathematics/college/ivkz8acxti8ogpapejlkt4e67kqf1q7swx.png)
This is the option B.