Question

Select the best answer to the word problem (Picture provided)

Answer 1

The answer is
`L_(t)=0.5L_(0)` ⇒ answer (b)

Explanation:

* Lets discuss the formula

- cosФ =
`\sqrt{(L_(t))/(L_(0))}`

- Now find
`L_(t)` in termas of cosФ and
`L_(0)`

* square the two sides

∴ cos²Ф =
`(L_(t))/(L_(0))`

* Multiply two sides by
`L_(0)`

∴ cos²Ф ×
`L_(0)` =
`L_(t)`

∵ Ф = 45°

∴
`L_(t)=cos^(2)45(L_(0))`

∵ cos45 = √2/2

∴ cos²Ф = (√2/2)² = 1/2 = 0.5

∴
`L_(t)=0.5L_(0)`