# Triangle Trig Question

• Jun 3rd 2008, 05:22 PM
~berserk
Triangle Trig Question
Last One!

A farmer has a triangular field with sides of 240 ft., 300 ft., and 360 ft. He wants to apply fertilizer to the field. If one 40-pound bag of fertilizer covers 6000 square feet, how many bags must he buy to cover the field.
I drew a diagram and have a feeling I need to use these equations
Law of Cosines
Area of a triangle (1/2 ab sinC)

I just don't know how I would go about it
• Jun 3rd 2008, 06:15 PM
sean.1986
Quote:

Originally Posted by ~berserk
Last One!

A farmer has a triangular field with sides of 240 ft., 300 ft., and 360 ft. He wants to apply fertilizer to the field. If one 40-pound bag of fertilizer covers 6000 square feet, how many bags must he buy to cover the field.
I drew a diagram and have a feeling I need to use these equations
Law of Cosines
Area of a triangle (1/2 ab sinC)

I just don't know how I would go about it

Use Cosine rule to get the angle opposite one of the sides.

240^2 = 300^2 + 360^2 - 2*300*360CosA

CosA = (300^2 + 360^2 - 240^2)/(2*300*360)

A = Cos^-1(3/4)

Area = 0.5*300*360Sin(Cos^-1(3/4)) = 35718 sq ft

35718 / 6000 = 5.953

Therefore he needs 6 bags.