if a=20 b=21 and cosC = 4/5 then sin B =
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Let the Triangle be ABC
We only need Cos C
Cos C=4/5=Adjecent/ Hypotenuse
So,
NOW applying Pythogoras Theorem
AB^2=AC^2-BC^2
=> AB^2= 25-16
=> AB=3
NOW AB is our Perpendicular
So,
SinB= Opposite/ Hypotenuse=3/5
We only need Cos C
Cos C=4/5=Adjecent/ Hypotenuse
So,
NOW applying Pythogoras Theorem
AB^2=AC^2-BC^2
=> AB^2= 25-16
=> AB=3
NOW AB is our Perpendicular
So,
SinB= Opposite/ Hypotenuse=3/5
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