In triangle ABC <B=90°,Ac=15cm and sin A=4/5 find the length of Bc? find cos A
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Answer:
Sin A=BC/AC
=BC/15
=4/5
That means...
BC=3×4=12
Cos A=AB/AC
AB=√AC²-BC²
=√15²-12²
=√225-144
=√81 =9
Therefore,
Cos A=AB/AC
=9/5 =3/5
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