Question

The law of cosines is used to find the measure of Z.

Answer 1

Answer:

C. 51º

Step-by-step explanation:

Answer 2

Answer:

C. $Z=51^{\circ}$

Step-by-step explanation:

We have been given a triangle. We are asked to find the measure of angle Z using Law of cosines.

Law of cosines: $c^2=a^2+b^2-2ab\cdot \text{cos}(C)$, where, a, b and c are sides opposite to angles A, B and C respectively.

Upon substituting our given values in law of cosines, we will get:

$16^2=19^2+18^2-2(19)(18)\cdot \text{cos}(Z)$

$256=361+324-684\cdot \text{cos}(Z)$

$256=685-684\cdot \text{cos}(Z)$

$256-685=685-685-684\cdot \text{cos}(Z)$

$-429=-684\cdot \text{cos}(Z)$

$\frac{-429}{-684}=\frac{-684\cdot \text{cos}(Z)}{-684}$

$0.627192982456=\text{cos}(Z)$

$\text{cos}(Z)=0.627192982456$

Now, we will use inverse cosine or arc-cos to solve for angle Z as:

$Z=\text{cos}^{-1}(0.627192982456)$

$Z=51.1566718^{\circ}$

$Z\approx 51^{\circ}$

Therefore, the measure of angle Z is approximately 51 degrees.