In ΔABC\Delta ABCΔABC, if a=18,b=24,c=30a=18, b=24, c=30a=18,b=24,c=30, find cosA\cos AcosA.
Using Cosine Rule: cosA=b2+c2−a22bc\cos A = \frac{b^2 + c^2 - a^2}{2bc}cosA=2bcb2+c2−a2 cosA=242+302−1822(24)(30)\cos A = \frac{24^2 + 30^2 - 18^2}{2(24)(30)}cosA=2(24)(30)242+302−182 cosA=576+900−3241440=11521440=0.8\cos A = \frac{576 + 900 - 324}{1440} = \frac{1152}{1440} = 0.8cosA=1440576+900−324=14401152=0.8
Standard Values:
sin 0 = 0, sin 30 = 0.5, sin 45 = 0.707, sin 60 = 0.866, sin 90 = 1
cos 0 = 1, cos 30 = 0.866, cos 45 = 0.707, cos 60 = 0.5, cos 90 = 0
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