## Elementary Geometry for College Students (6th Edition)

$β = 40˚$
Let $x =$ the one of the unknown angle $\frac{sin(x)}{7} = \frac{sin(70)}{7}$ $sin(x) = sin(70)$ $x = sin^{-1}(sin(70))$ $x = sin^{-1} (sin(0.9396))$ by Graphic Display Calculator / GDC $x = 70˚$ 2. Add the first 2 known angles and subtract from $180˚$ to solve for $β$ $β + 70 + 70 = 180$ $β + 140 = 180$ $β = 40˚$ Therefore, $β = 40˚$.