Question

Use the law of cosines to find the value of cos theta. round your answer to two decimal places

Answer 1

Answer:

The correct answer option is B. 0.21.

Step-by-step explanation:

We are to find the value of $cos \theta$ using the law of cosines.

We know that the formula of the cosine rule is given by:

$c ^ 2 = a ^ 2 + b ^ 2 - 2 a b cos C$

So substituting the given values in the above formula:

$10.9 ^ 2 = 5.8 ^ 2 + 10.5 ^ 2 - 2 (5.8) (10.5) cos C$

$118.81=33.64+110.25-121.8cosC$

$118.81 - (33.64+110.25) = -121.8cosC$

$118.81-143.86=-121.8cosC$

$cosC=\frac{-25.05}{-121.8}$

cos C = 0.21