Find the length of line DC

Geometry Level pending

In the diagram shown above, A E = 32 , D E = 24 AE=32,DE=24 and A B = 9 AB=9 . Find D C DC correct to 5 5 decimal places.


The answer is 31.53846.

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1 solution

By pythagorean theorem, we have

A D = 2 4 2 + 3 2 2 = 40 AD=\sqrt{24^2+32^2}=40

sin E D A = 32 40 \sin \angle EDA=\dfrac{32}{40} \implies E D A = sin 1 ( 32 40 ) \angle EDA=\sin^{-1}\left(\dfrac{32}{40}\right)

tan B D A = 9 40 \tan \angle BDA=\dfrac{9}{40} \implies B D A = tan 1 ( 9 40 ) \angle BDA=\tan^{-1}\left(\dfrac{9}{40}\right)

E D C = E D A B D A = sin 1 ( 32 40 ) tan 1 ( 9 40 ) \angle EDC=\angle EDA - \angle BDA=\sin^{-1}\left(\dfrac{32}{40}\right)-\tan^{-1}\left(\dfrac{9}{40}\right)

cos E D C = 24 D C \cos \angle EDC=\dfrac{24}{DC}

D C = 24 cos E D C = 24 cos [ sin 1 ( 32 40 ) tan 1 ( 9 40 ) ] DC=\dfrac{24}{\cos \angle EDC}=\dfrac{24}{\cos\left[\sin^{-1}\left(\dfrac{32}{40}\right)-\tan^{-1}\left(\dfrac{9}{40}\right)\right]} \approx 31.53846 \boxed{31.53846}

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