Question

The law of Cosines Is......​

Answer 1

C

Explanation:

a² + b² - 2abcosC = c² ( subtract a² + b² from both sides )

- 2abcosC = c² - a² - b² ( multiply through by - 1 )

2abcosC = a² + b² - c²

a, b, c are the sides opposite vertices A, B, C

here a = 4 , b = 3 , c = 2 , then

a² + b² - c²

= 4² + 3² - 2²

= 16 + 9 - 4

= 25 - 4

= 21

Answer 2

Answer:
`\Large\boxed{C.~21}`

Explanation:

The goal of the question

Find the value of 2abcosC

Given information

a = 4

b = 3

c = 2

Given formula (Law of Cosine)

`c^2=a^2+b^2-2abcosC`

Substitute values into the formula (Leave 2abcosC as it is)

`(2)^2=(4)^2+(3)^2-2abcosC`

Simplify the exponents

`4=16+9-2abcosC`

Simplify by addition

`4=25-2abcosC`

Add 2abcosC on both sides

`4+2abcosC=25-2abcosC+2abcosC`

`4+2abcosC=25`

Subtract 4 on both sides

`4 + 2abcosC-4=25-4`

`\Large\boxed{2abcosC=21}`

Hope this helps!! :)

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