Question

Select the angle that correctly completes the law of cosines for this triangle

Answer 1

Option 'B'

Explanation:

The law of cosines states that given a triangle with sides a, b, c, then:

`c^(2) =a^(2)+b^(2) -2abcos(y)` where 'y' is the opposite angle to the side 'c'.

In this case, given that the equation is:
`15^(2) =8^(2) + 17^(2) -2(8)(17)cos(y)` we can clearly see that c=15, and the opposite angle to 'c' is 62 degrees.

The correct option is Option 'B'

Answer 2

B. 62°

EXPLANATION

The cosine rule is given by:

`{b}^(2) + {c}^(2) - 2(bc) \cos(A) = {a}^(2)`

where A is the angle that is direct opposite to the side length which is 'a' units.

The given relation is:

`8^(2) + {17}^(2) - 2(8)(17) \cos( - ) = {15}^(2)`

The missing angle should be the angle directly opposite to the side length measuring 15 units.

From the diagram the missing angle is 62°