A local naturalist says that a triangular area on the north side of a pond is a turtle habitat. The lengths of the sides of this area are 15 meters, 25 meters, and 36 meters. Which expression gives the measure of the angle between the sides of the habitat that measure 15 meters and 25 meters?

Question

anonymous · Answer

|dw:1365813129400:dw|

use law of cosine

directrix · Answer

Law of Cosines: The square of any side of a triangle is equal to the sum of the squares of the other two sides MINUS twice the product of those sides and the cosine of the angle included between those sides.

directrix · Answer

|dw:1365814836985:dw|

directrix · Answer

36² = 15² + 25² - 2*15*25*cos(x)

@aagard 

I don't know how much simplification needs to be done on the equation because I don't know the options. (Which expression gives the measure of the angle) 
So, when you are online here, let us know.