Question

the equation \\(cos^{-1}\left(\frac{3.4}{10}\
ight) = x\\) can be used to determine the measure of angle bac.

diagram of right triangle abc with right angle at c, ac = 3.4 cm, ab = 10 cm

what is the degree measure of angle bac? round to the nearest whole degree.

• 18°
• 20°
• 70°
• 71°

Explanation:

Step1: Calculate the value of $\cos^{-1}(\frac{3.4}{10})$

Use the inverse - cosine function.
$$x=\cos^{-1}(\frac{3.4}{10})$$

Step2: Evaluate the expression

Using a calculator, $\frac{3.4}{10} = 0.34$. Then $\cos^{-1}(0.34)\approx70^{\circ}$ (since $\cos(70^{\circ})\approx0.3420$).

Answer:

C. $70^{\circ}$