If sin 23° = a/b, then the value of sec 23° - sin 67° is
a² + b² / 2ab
b² - a² / ab
\( \frac{a^{2}}{b \sqrt{b^{2} + a^{2}}} \)
\( \frac{a^{2}}{b \sqrt{b^{2} - a^{2}}} \)
What is the central angle corresponding to the sector indicating the expenses incurred on health?