ABC ∆ where Angle A =90° , AB = 12 m, AC = 9 m . Find BC ?
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Answer:
Step-by-step explanation:
From figure: △ABCis a right angled triangle
AC
2
=BC
2
+AB
2
AC
2
=(5)
2
+(12)
2
AC
2
=25+144
AC
2
=169=(13)
2
or AC=13
Now from figure,
i.cosA=
AC
AB
=
13
12
ii.cscA=
BC
AC
=
5
13
iii.cosC=
AC
BC
=
13
5
iv.cscC=
AB
AC
=
12
13
Hence, proved.
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