The pythagorean theorem says that a² + b² = c²
You're given the b and the c so substitute the values in: a² + 12² = 15²
a² + 144 = 225; subtract 144 from both sides
a² = 81; square root each side
a = 9, or choice C
The answer to this question is 0.16666666666
Step-by-step explanation:

Do this.
38 divided by two
then use the equation
38=5+2x
Dy/dx = (ycos(x))/(1 + y²)
(1 + y²)/y dy = cos(x) dx
(1/y + y) dy = cos(x) dx
Integrating:
ln(y) + y²/2 = sin(x) + c
ln(1) + 1/2 = sin(0) + c
c = 1/2
Thus,
ln(y) + y²/2 = sin(x) + 1/2