help I need to find lengths
$A$, $B$, $C$, and $D$ are points on a circle, and segments $\overline{AC}$ and $\overline{BD}$ intersect at $P$, such that $AP=8$, $PC=2$, and $BD=5$. Find $BP$, given that $BP < DP.$
To find BP, you can use Ptolemy's Theorem which applies to cyclic quadrilaterals. The theorem states that in such a quadrilateral, AC×BD=AB×CD+BC×AD. First, AC=AP+PC=10 and BD=5. We can express AB and AD in terms of BP and DP since AB=BP+DP and AD=BP−DP. Applying Ptolemy's theorem: 10×5=(BP+DP)×2+10×(BP−DP) 50=2BP+2DP+10BP−10DP 50=12BP−8DP 12.5=3BP−2DP Since BP<DP, DP−BP>0. Let x=DP−BP. Then DP=BP+x. Substitute into 3BP=12.5+2DP: 3BP=12.5+2(BP+x) 3BP=12.5+2BP+2x BP=12.5+2x BP−2x=12.5 Also, x=DP−BP: x=DP−(12.5+2x) x=−12.5−2x 3x=−12.5 x=−12.53 x=−256 Finally, BP=12.5+2x BP=12.5−253 BP=12.53 BP=256 So BP=256.
Ptolemy has nothing to do with this problem. Also, 5 - 25/6 = 5/6 < 25/6 so clearly that cannot be BP.