Answer:
The answer is [tex]L_{t}=0.5L_{0}[/tex] ⇒ answer (b)
Step-by-step explanation:
* Lets discuss the formula
- cosФ =[tex]\sqrt{\frac{L_{t}}{L_{0}}}[/tex]
- Now find [tex]L_{t}[/tex] in termas of cosФ and [tex]L_{0}[/tex]
* square the two sides
∴ cos²Ф = [tex]\frac{L_{t}}{L_{0}}[/tex]
* Multiply two sides by [tex]L_{0}[/tex]
∴ cos²Ф × [tex]L_{0}[/tex] = [tex]L_{t}[/tex]
∵ Ф = 45°
∴ [tex]L_{t}=cos^{2}45(L_{0})[/tex]
∵ cos45 = √2/2
∴ cos²Ф = (√2/2)² = 1/2 = 0.5
∴ [tex]L_{t}=0.5L_{0}[/tex]
