Question

A=2 b=2 c=1 Find the value of 2abcosC

Answer 1

`2abCosC = 1`

Explanation:

The cosine rule is

=>
`a^2= b^2+c^2-2abCosC`

For 2abCosC, it becomes

=>
`2abCosC = b^2+c^2-a^2`

=>
`2abCosC = (2)^2+(1)^2-(2)^2`

=>
`2abCosC = 1`