To find the cosine of an angle that has a sine of \(340\sqrt{20}\) and is in Quadrant II, we can use the Pythagorean identity:
\[ \sin^2 \theta + \cos^2 \theta = 1 \]
Given that \( \sin \theta = 340\sqrt{20} \), we first compute \( \sin^2 \theta \):
\[ \sin^2 \theta = (340\sqrt{20})^2 = 340^2 \cdot 20 = 115600 \cdot 20 = 2312000 \]
Next, we can plug this value into the Pythagorean identity:
\[ 2312000 + \cos^2 \theta = 1 \]
This gives us:
\[ \cos^2 \theta = 1 - 2312000 \]
This can be simplified to:
\[ \cos^2 \theta = -2311999 \]
Because \( \cos^2 \theta \) cannot be negative, it appears that there has been a confusion in interpreting the sine value.
Typically, the sine of an angle ranges between -1 and 1. Thus, a sine value of \(340\sqrt{20}\) is far greater than 1, which is not possible for any angle in standard trigonometric definitions.
Please recheck the given sine value, as it seems incorrect and impossible within the framework of trigonometric functions.