The question is asking, If a triangle has the sides d (19.6metres), e (13.2 metres) and f (10.4 metres) What is the size of the angle EDF? Help please?
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side d is that one which is opposite angle EDF
cosine rule is d^2 = e^2 +f^2 -2ef cos EDF
so, 384.16 = 174.24 + 108.16 -137.28 cosEDF
so, cos EDF = 0.7412...so angle EDF = 42.16
cosine rule is d^2 = e^2 +f^2 -2ef cos EDF
so, 384.16 = 174.24 + 108.16 -137.28 cosEDF
so, cos EDF = 0.7412...so angle EDF = 42.16