For a graph?
If it is for a graph I can help, otherwise you need more information.
<u>Answer</u> : The demonstration is below :)
Step-by-step explanation :
<u>We use Pythagoras' </u><u>theorem </u><u>:</u>
- In the triangle ABC we have :
AB² = AC² - BC² = 15² - 9² = 144 = 12²
- In the triangle ABD we have :
DB² = AD² - AB² = 13² - 12² = 5²
cos(a) = BD/AD = 5/13
C because x represent the cost of books while 2 can be an additional price for the pens
