Answer:
The first option (5.7km)
Step-by-step explanation:
Since we have a right angle triangle and we know two of its sides we can easily find out the thirds side (the value of d) by using the Pathagoras Theorem. In our case 7 and d are our legs and the hypotenuse is equal to 9, so...
(Based on the Pathagoras Theorem)
[tex]c^{2} = a^{2} + b^{2}[/tex]
[tex]9^{2} = 7^{2} + d^{2}[/tex]
[tex]d^{2} = 9^{2} - 7^{2} \\d^{2} = 81 - 49\\d^{2} = 32\\d = \sqrt{32}\\[/tex]
d ≈ 5.7km
There for aproximate distance across the lake is equal to 5.7km
