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 #3
avatar+26377 
+2

2.

In cyclic quadrilaterla ABCD, AB=2, BC=3, CD=10, and DA=6.

Let P be the intersection of lines AB and CD.

Find the length BP.

\(\text{Let $BP =x$} \\ \text{Let $PA =2+x$} \\ \text{Let $PC =y$} \\ \text{Let $PD =10+y$} \)


\(\text{Let $\angle BPC = P $} \\ \text{Let $\angle CBP = B $} \\ \text{Let $\angle ABC = 180^\circ -B $} \\ \text{Let $\angle ADC = 180^\circ - \angle ABC =180^\circ-(180^\circ -B)=B $} \)

 

1.

Intersecting secants theorem:

see: https://en.wikipedia.org/wiki/Intersecting_secants_theorem

\(\begin{array}{|rcll|} \hline \mathbf{BP\cdot PA} &\mathbf{=}& \mathbf{PC\cdot PD} \quad | \quad \text{Intersecting secants theorem} \\\\ x\cdot (2+x) &=& y\cdot (10+y) \\ \hline \end{array} \)

 

2.
sin-theorem:

\(\begin{array}{|lrcll|} \hline 1. & \dfrac{\sin(P)}{3} &=& \dfrac{\sin(B)}{y} \\ & \dfrac{\sin(P)}{\sin(B)} &=& \dfrac{3}{y} \\\\ 2. & \dfrac{\sin(P)}{6} &=& \dfrac{\sin(B)}{2+x} \\ & \dfrac{\sin(P)}{\sin(B)} &=& \dfrac{6}{2+x} \\ \hline & \dfrac{\sin(P)}{\sin(B)} = \dfrac{3}{y} &=& \dfrac{6}{2+x} \\\\ & \dfrac{3}{y} &=& \dfrac{6}{2+x} \\\\ & \dfrac{y}{3} &=& \dfrac{2+x}{6} \\\\ & y &=& \dfrac{3}{6}\cdot(2+x) \\\\ & \mathbf{y} & \mathbf{=}& \mathbf{\dfrac{1}{2}\cdot(2+x)} \\\\ & x\cdot (2+x) &=& y\cdot (10+y) \quad | \quad y = \dfrac{1}{2}\cdot(2+x) \\\\ & x\cdot (2+x) &=& \dfrac{1}{2}\cdot(2+x)\cdot \left(10+\dfrac{1}{2}\cdot(2+x)\right) \\\\ & x &=& \dfrac{1}{2} \cdot \left(10+ \dfrac{1}{2}\cdot(2+x) \right) \quad | \quad \cdot 2 \\\\ & 2x &=& 10+ \dfrac{1}{2}\cdot(2+x) \quad | \quad \cdot 2 \\\\ & 4x &=& 20+ 2+x \\\\ & 3x &=& 22 \\\\ & x &=& \dfrac{22}{3} \\\\ & \mathbf{ x } & \mathbf{=} & \mathbf{7.\bar{3}} \\ \hline \end{array}\)

 

laugh

Mar 19, 2019
 #2
avatar+2440 
+4

Well now you have four answers, and you are too bloody dumb to know if any of them are correct.

 

 Lets’ see ... 

Rom’s answer agrees with CPhill’s, which he posted here: https://web2.0calc.com/questions/could-you-help-me-with-this-please-its-practicing    (When you repeat questions, include the link to you previous posts.)

 

Rom’s answer is presented in pristine LaTex (not ASCII slop), which probably makes it consistent with your online text (or book), but you are not going to understand Rom’s answer any more than you understood CPhill’s answer. The reasons for this are appended to your previous post.   

 

Keep in mind, if you are too lazy, or put-off, to go back to the prerequisites, you are not going to learn or understand this material. You just are wasting everyone’s time –including your own.indecision    

 

 

GA

Mar 19, 2019

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