Question

Calculate cos 0 to two decimal places

Answer 1

We can use the law of cosines as follows:

`7^2 = 8^2+10^2-2\cdot 8 \cdot 10 \cdot \cos(\theta)`

We can rewrite this equation as

`49 = 164-160 \cdot \cos(\theta) \iff 160 \cdot \cos(\theta) = 115 \iff \cos(\theta)=(115)/(160)\approx 0.72`

Answer 2

For this case we have by definition of the Cosines Law that:

`7 ^ 2 = 10 ^ 2 + 8 ^ 2-2 (10) (8)`* cosΘ

`49 = 100 + 64-160`cosΘ

`49 = 164-160`cosΘ

`49-164 = -160`cosΘ

`-115 = -160`cosΘ

`115 = 160`cosΘ

cosΘ=
`\frac {115} {160} = 0.71875`

Rounding off we have, 0.72

ANswer:

Option C