if Sin A = 3/4 , Calculate Cos A
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Answer:
Step-by-step explanation:
Given, sinA=
4
3
⇒
DC
BC
=
4
3
⇒BC=3k and AC=4k
where k is the constant of proportionality.
By Pythagoras theorem, we have
AB
2
=AC
2
−BC
2
=(4k)
2
−(3k)
2
=7k
2
⇒AB=
7
k
So, cosA=
AC
AB
=
4k
7
k
=
4
7
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