We are given a circle with center at some point. We have three points on the circumference of the circle: $R$, $S$, and $T$. We are given that the measure of the arc $RT$ is $58^\circ$. We are asked to find the value of $x$, where $x^\circ$ is the measure of the arc $RS$.

GeometryCirclesArcsAnglesInscribed Angle TheoremIsosceles Triangle
2025/4/29

1. Problem Description

We are given a circle with center at some point. We have three points on the circumference of the circle: RR, SS, and TT. We are given that the measure of the arc RTRT is 5858^\circ. We are asked to find the value of xx, where xx^\circ is the measure of the arc RSRS.

2. Solution Steps

Since SS is on the circle and SRSR and STST are radii, triangle RSTRST is an isosceles triangle with SR=STSR = ST.
The inscribed angle theorem states that the measure of an inscribed angle is half the measure of its intercepted arc. The inscribed angle RST\angle RST intercepts the arc RTRT, which has measure 5858^{\circ}. Therefore, RST=12(58)=29\angle RST = \frac{1}{2} (58^\circ) = 29^\circ.
Since triangle RSTRST is isosceles with SR=STSR = ST, SRT=STR\angle SRT = \angle STR.
Let SRT=STR=θ\angle SRT = \angle STR = \theta.
In triangle RSTRST, the sum of the angles is 180180^\circ.
SRT+STR+RST=180\angle SRT + \angle STR + \angle RST = 180^\circ
θ+θ+29=180\theta + \theta + 29^\circ = 180^\circ
2θ=18029=1512\theta = 180^\circ - 29^\circ = 151^\circ
θ=1512=75.5\theta = \frac{151^\circ}{2} = 75.5^\circ
The measure of central angle RSO\angle RSO is xx, so the measure of arc RSRS is xx^{\circ}.
Since the angle RSO\angle RSO is the central angle that subtends arc RSRS, we know that the measure of RSO\angle RSO is equal to the measure of the arc RSRS. Thus RSO=x\angle RSO = x^\circ.
Since SR=STSR=ST, SRT=STR\angle SRT = \angle STR, SRT=STR=(18058)/2=122/2=61\angle SRT = \angle STR = (180-58)/2 = 122/2 = 61. Since OR=OSOR = OS, OSROSR is isosceles, so ORS=OSR=x\angle ORS = \angle OSR = x
RST=58/2=29\angle RST = 58/2 = 29.
Since SS is at the center, the angle RSTRST = arc RTRT. The value is
5

8. Since SR = ST, $\angle SRT = \angle STR = (180-x)/2$

Also, we are given RTS\angle RTS is 5858^\circ, then RST\angle RST is 1/21/2 of this 2929^\circ.
We see that RST=29\angle RST = 29.
R=T\angle R = \angle T.
So, STR=SRT=x\angle STR = \angle SRT = x.
We have, RSST=58x\frac{RS}{ST} = \frac{58^\circ}{x}
Since, SR=STSR=ST
1=58x1 = \frac{58}{x}.
The central angle that intercepts the arc RSRS is xx.
Since RTS=58\angle RTS = 58^\circ, then the measure of arc RTRT = 58
We know that RST\angle RST is an inscribed angle that intercept arc RTRT. Therefore RST=58/2=29\angle RST = 58^\circ/2 = 29^\circ.
Since SR=STSR = ST, TRS=SRT=(180x)/2\angle TRS = \angle SRT = (180-x)/2
RTS+RTS=180\angle RTS + \angle RTS = 180^\circ
x+x+x/2=58/2=29x + x + x/2= 58/2 = 29^{\circ}.
Since the central angle ROT=58ROT=58^\circ, we are also aware that arc RT=58RT = 58^{\circ}.
Since triangle RSORSO is isosceles with OR=OSOR = OS, ORS=OSR=x\angle ORS = \angle OSR = x
However, the diagram indicates that SS is not the center. Then x=58x=58. Since the segments SRSR and STST are congruent, that would make triangle SRTSRT is an isoceles triangle.
The RTS\angle RTS is 5858^{\circ}. So the other angles are (18058)/2(180-58)/2 = 6161^{\circ}. Thus, x=61x=61

3. Final Answer

61

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