Question

What is the value of cos0 ?

Answer 1

`(9)/(10)`

Explanation:

The Law of Cosines works for any triangle and is given by:

`c^2=a^2+b^2-2ab\cos \gamma`, where
`a`,
`b`, and
`c` are the sides of the triangle and
`\gamma` is the angle opposite to
`c`.

In the given triangle, assign the variables:

• 
  `c\implies 10`
• 
  `a\implies 10`
• 
  `b\implies 18`

Substituting these variables, we have:

`10^2=10^2+18^2-2(10)(18)\cod \cos \gamma,\\100=100+324-360\cdot \cos \gamma,\\100=424-360\cos \gamma,\\-324=-360\cos\gamma,\\\cos \gamma =(-324)/(-360)=\boxed{(9)/(10)}`