Angle of Elevation at Trigonometry Forum

Please help to solve this problem:
The angle of elevation of a point C from a point B is 29⁰42'; the angle of elevation of C from another point A 31.2 m directly below B is 59⁰23'. How high is C from the horizontal line through A?

Jhun Vert Tue, 04/18/2017 - 14:28

$\alpha = 90^\circ - 59^\circ 23' = 30^\circ 37'$

$\beta = 90^\circ + 29^\circ 42' = 119^\circ 42'$

$\theta = 180^\circ - \alpha - \beta = 29^\circ 41'$

$\dfrac{x}{\sin \beta} = \dfrac{31.2}{\sin \theta}$

$x = 54.73 ~ \text{m}$

$y = x \sin 59^\circ 23'$

$y = 47.098 ~ \text{m}$ answer

esmilitar Tue, 04/18/2017 - 20:27

Thanks a lot sir its a great help.

esmilitar Tue, 04/18/2017 - 20:42

Thanks a lot sir its a great help. I had another solution using tangent got the same answer..

esmilitar Tue, 04/18/2017 - 22:25

AB=A'B'=31.2m
AA'=BB'=X
A'C=y=31.2 + y'
y=31.2 + y'

tan 29⁰42'=y'/x

x = y'/ tan 29⁰42'
tan 59⁰23'=y/x
tan 59⁰23'=(31.2+y')/(y'/(tan 29⁰42')
(tan 59⁰23')(y')/(tan29⁰42')=31.2 +y'
2.9625y'-y'=31.2
y'=31.2/1.9625
y'=15.898m
y=31.2 + 15.898
y=47.098m Ans

Jhun Vert Wed, 04/19/2017 - 06:28

Yes. also an straightforward solution.

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$\alpha = 90^\circ - 59^\circ

Thanks a lot sir its a great

Thanks a lot sir its a great

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Yes. also an straightforward

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