Show that the equation of the straight line through the origin angle `varphi` with the line `y=m x+b\ i s y/x=(m+-t a nvarphi)/(1+-m\ t a nvarphi)`

Explanation

Let the equation of the line passing through the origin be `y=m_1​x`


If this line makes an angle of `theta` with line y=mx+c, then angle `theta` is given by
`tan theta=|(m_1-m)/(1+m_1m)|`


⇒`tan theta=∣(y/x-m)/(1+y/xm)|`


⇒`tan theta=+-∣(y/x-m)/(1+y/xm)|`

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