Let the base of the board is x feet away from the wall .
And the hypotenuse, which is represented by the length of the board be 15 foot .
So here we have adjacent represented by the base and the hypotenuse .
And cosine function relates adjacent and hypotenuse , which is
[tex]cos 60 = \frac{15}{x}[/tex]
And the value of cos 60 is half .
[tex]\frac{1}{2}= \frac{x}{15}[/tex]
Performing cross multiplication
[tex]2x=15[/tex]
Dividing both sides by 2
[tex]x=7.5 ft[/tex]
Correct option is A .
