Hello there. To solve this question, we have to remember some properties about circles and theorems relating chords.
Given the following diagram:
And the lengths of AP = 3.5, PD = 6 and PC = 4, we want to determine BP and BC.
Okay. First, we'll need the following theorem:
The theorem says that for the chords AC and BD, intersecting at E, it is true that
![AE\cdot EC=BE\cdot ED](https://img.qammunity.org/2023/formulas/mathematics/college/c4h61ipgthoefzpirhfu83g4ayjyfinnow.png)
In this case, we have the lengths of three of the factors, therefore:
![BP\cdot PC=AP\cdot PD](https://img.qammunity.org/2023/formulas/mathematics/college/bq6xwcyeivq4agqprvpsmsea90tcm8lasv.png)
Plugging the values, we get
![BP\cdot4=3.5\cdot6](https://img.qammunity.org/2023/formulas/mathematics/college/ifo51g10gsqalp7xr7p9sdvz86x9hukkua.png)
Divide both sides of the equation by a factor of 4
![BP=3.5\cdot(6)/(4)=3.5\cdot1.5=5.25](https://img.qammunity.org/2023/formulas/mathematics/college/81xtvh5vwk65qs1fnbl60llhys7rmt25ny.png)
Finally, we know that
![BC=BP+PC](https://img.qammunity.org/2023/formulas/mathematics/college/itjzs248m0p7250lrrw1knf3qv3l1z2qdv.png)
Hence we get
![BC=5.25+4=9.25](https://img.qammunity.org/2023/formulas/mathematics/college/4p3u3ai1lvlabi3g1odzklkp8xqbeuylf5.png)
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