Question

The law of cosines is a2 +62 - 2abcosC = (2. Find the value of 2abcosC.

Answer 1

Answer:

A. 37

Step-by-step explanation:

Answer 2

Answer:

$2abcosC = 37$

Step-by-step explanation:

Given

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

Required

$2abcosC$

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

Add $2abcosC$ to both sides

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

$a^2 + b^2 = c^2+2abcosC$

Subtract $c^2$ from both sides

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

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

From the attachment:

$a = 4$ $b = 5$ and $c = 2$

So, we have:

$4^2 + 5^2 -2^2= 2abcosC$

$16 + 25 -4= 2abcosC$

$37= 2abcosC$

i.e.

$2abcosC = 37$