In quadrilateral BCED, we have BD = 11, BC = 9, and CE=2. Sides BD andCE are extended past B and C, respectively, to meet at point A. If AC = 28 and AB = 24, then what is DE?
+23246 In triangle(ABC), you have: AB = 24, AC = 28. and BC = 9.
Since you have the three sides, use the Law of Cosines to find angle(A)
a2 = b2 + c2 - 2·b·c·cos(A)
92 = 282 + 242 - 2·28·24·cos(A)
Solve this for angle(A).
Now, look at triangle(ADE).
AD = 35, AE = 30, and you have angle(A) from above.
Use the Law of Cosines for this triangle.
a2 = b2 + c2 - 2·b·c·cos(A)
a2 = 352 + 302 - 2·35·30·cos(A)
