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In the diagram below, $\angle PQR = \angle PRQ = \angle STR = \angle TSR$, $RQ = 8$, and $SQ = 2$. Find $PQ$.

 

[asy]
pair A,B,C,D,E;
A = (0, 0.9);
B = (-0.4, 0);
C = (0.4, 0);
D = (-0.275, 0.16);
E = (0.11, 0.65);
draw(A--B);
draw(A--C);
draw(B--C);
draw(B--E);
draw(C--D);
label("$P$",A,N);
label("$Q$", B, S);
label("$R$", C, S);
label("$S$", D, S);
label("$T$", E, W);
[/asy]

 Jul 12, 2021
 #1
avatar+26396 
+3

In the diagram below,
PQR=PRQ=STR=TSR=A,RQ=8,  and SQ=2.
Find PQ.

 

 

Let QPR=1802ALet RQT=1802ALet TRS=1802ALet PTQ=180ALet PQ=x Let QR=QT=8 Let TR=SR=y 

 

ST=QTSQST=82ST=6

 

In [QPT]:sin(1802A)8=sin(180A)xsin(2A)8=sin(A)xsin(2A)sin(A)=8x(1)In [QTR]:sin(1802A)y=sin(A)8sin(2A)y=sin(A)8sin(2A)sin(A)=y8(2)In [QSR]:sin(1802A)6=sin(A)ysin(2A)6=sin(A)ysin(2A)sin(A)=6y(3)

 

(2)=(3):y8=6yy2=48y2=163y=43(2)=(1):y8=8xxy=64x=64yx=6443x=163x=16333x=1633

 

 

PQ=1633

 

laugh

 Jul 12, 2021
 #2
avatar+1693 
+2

Nice work, heureka, as always!!!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

QS = TU = 2

QT = QR = 8

QW = 5

RV = 4

TW = sqrt(QT2 - QW2)

RT = sqrt(TW2 + RW2)

RW / RT = RV / PR

PQ = PR = (RT * RV) / RW

civonamzuk  Jul 14, 2021

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