A geometry problem by Mohammad Khaza

Geometry Level 2

Let sin x = 3 5 \sin x =\dfrac35 , n = tan x sin x , m 2 n 2 = 4 m n n = \tan x - \sin x , m ^2 - n^2 = 4\sqrt{mn} .

Find the value of n n such that tan x 0 \tan x \geq 0 .

1/9 8/19 2/7 3/20

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2 solutions

Nazmus Sakib
Sep 29, 2017

sin x = A B A C \sin x = \dfrac{AB}{AC}

= 3 5 = \dfrac{3}{5}

tan x = A B B C \tan x = \dfrac{AB}{BC}

Suppose B C = x BC = x

Applying Pythagorean theorem

x 2 + 3 2 = 5 2 x^2 + 3^2 = 5^2

or, x 2 + 9 = 25 x^2 + 9 = 25

or, x 2 = 25 9 x^2 = 25 - 9

or, x 2 = 16 x^2 = 16

or, x = ± 4 x = \pm4

Now,

B C = x = ± 4 BC = x = \pm4

tan θ = 3 4 \tan \theta = \dfrac{3}{4}

So n = tan x sin x n = \tan x - \sin x

= 3 4 3 5 = \dfrac{3}{4} - \dfrac{3}{5}

= 15 12 20 = 3 20 = \dfrac{15 - 12}{20} = \dfrac{3}{20}

thanks for posting a solution.

Mohammad Khaza - 3 years, 8 months ago
Mohammad Khaza
Jun 26, 2017

sinx=3/5

or, sinx^2=9/25

or, 1-cosx^2=9/25

or,cosx^2=1-9/25

or,cosx^2=16/25

or, cosx[=4/25 [tanx>/0]

  now, tanx=sinx/cosx

      or,tanx=3/5 x 5/4

       or, tanx=3/4

so,   n=tanx-sinx

         =3/4-3/5

         =3/20

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