Answer:
Explanation:
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 cos 60=15/x
And the value of cos 60 is half .
Performing cross multiplication
1/2=15/x
Dividing both sides by 2
x=7.5ft