Let’s look at how to use trigonometric identities to calculate missing sides. \({sin~θ} = \frac {opposite} {hypotenuse}\) \({cos~θ} = \frac {adjacent} {hypotenuse ...

frac{4^2 + 6.9^2 - 4.2^2}{2 \times 4 \times 6.9}\) \(\cos{y} = 0.8327898 \dotsc\). Do not round this answer yet. To calculate the angle use the inverse cos button on the calculator (\(\cos^{-1}\)).