Answer:
A. 16.55
Explanation:
What we know is the angle of 38° and the hypotenuse is 21. Before we find x (side b), we have to find side a first. TO find that multiply the sine of 38 by 21.
21 * sin(38)
sin(38) calculates to 0.615661475.
21 * 0.615661475
Multiply 21 by 0.615661475
side a = 12.928890975
Now to find x. Use this to find x: √21² - 12.928890975²
√21² - 12.928890975²
Square both numbers
√441 - 167.156221843
Subtract 167.156221843 from 441
√273.843778157
Find the square root of 273.843778157
x ≈ 16.548225831
x ≈ 16.55, so the answer is A.