the angles of elevation of the top of a tower from two points at a distance of 4 metre and 9 metre from the base of the tower and in the same straight line with it are complementary prove that the height of the tower is 6 metre
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Given :
α and β are Complimentry angles.
BC = 4 m
CD = 5 m
BD = BC + CD = 4 + 5 = 9 m
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To Prove :
Height of Tower be 6 m
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Proof :
In ΔABC
Tanα = AB/BC
Tanα = AB/4 ........(1)
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Now In Δ ABD
Tanβ = AB/BD
As α and β are Complimentry angles
⇒Tan(90° - α) = AB/9
⇒Cotα = AB/9
⇒1/Tanα = AB/9
★ Put value of Tanα
⇒1/AB/4 = AB/9
⇒4/AB = AB/9
⇒4*9 = AB*AB
⇒36 = AB²
⇒AB = √36
⇒AB = 6 m
∴ So, height is 6m
Hence Proved
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