## Thinking Mathematically (6th Edition)

$A \approx 58^o$
RECALL: In a right triangle, $\sin{A} = \dfrac{\text{length of opposite side}}{\text{length of hypotenuse}}$ $\cos{A} = \dfrac{\text{length of adjacent side}}{\text{length of hypotenuse}}$ $\tan{A} = \dfrac{\text{length of opposite side}}{\text{length of adjacent side}}$ Use the sine formula above to obtain: $\sin{A} = \dfrac{17}{20}$ Use the inverse sine function to obtain: $A = \sin^{-1}{(\frac{17}{20})} \\A = 58.21166938^o \\A \approx 58^o$