If $5\tan\theta-4=0,$ then the value of $\frac{5\sin\theta-4\cos\theta}{5\sin\theta+4\cos\theta}$ is:
A$\frac{5}{3}$
B$\frac{5}{6}$
C$\ 0$
D$\frac{1}{6}$
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C$\ 0$
Given that: $5\tan\theta-4=0.$We have to find the value of the following expression
$\frac{5\sin\theta-4\cos\theta}{5\sin\theta+4\cos\theta}$
$$Since $5\tan\theta-4=0$ $\Rightarrow \tan\theta =\frac{4}{5}$
$\tan\theta=\frac{\text{Perpendicular}}{\text{Base}}$
We know that:
$\Rightarrow \text{Base}=5$
$\Rightarrow{\text{perpendicular}}=4$
$\Rightarrow{\text{Hypotenuse=}\sqrt{\text{(Perpendicular)}^2+(\text{Base)}^2}}$
$\Rightarrow{\text{Hypotenuse=}}\sqrt{16+25}$
$\Rightarrow{\text{Hypotenuse=}}\sqrt{41}$
Since $\sin\theta =\frac{{\text{Perpendicular}}}{\text{Hypotenuse}}$ and $\cos\theta=\frac{\text{Base}}{{\text{Hypotenuse}}}$
Now we find
$\frac{5\sin\theta-4\cos\theta}{5\sin\theta+4\cos\theta}$
$=\frac{5\times\frac{4}{\sqrt{41}}-4\times\frac{5}{\sqrt{41}}}{5\times\frac{4}{\sqrt{41}}+4\times\frac{5}{\sqrt{41}}}$
$=\frac{\frac{20}{\sqrt{41}}-\frac{20}{\sqrt{41}}}{\frac{20}{\sqrt{41}}+\frac{20}{\sqrt{41}}}$
$=0$
Hence the correct option is $(c)$
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