In the figure, if $MR=MK$, the measure of arc $MK$ is 130 degrees, and measure of arc $MQ$ is 28 degrees, then what is $\angle RPK$, in degrees?
Since \(MR = MK\) and \(\overset{\frown}{MK} = 130°\) , \(\overset{\frown}{MR} = 130°\)
\(\overset{\frown}{MK} +\overset{\frown}{KR} +\overset{\frown}{MR} =360°\)
Replace \(\overset{\frown}{MK}\) with 130° and \(\overset{\frown}{MR}\) with 130°
\(130°+\overset{\frown}{KR}+130°=360° \\~\\ \overset{\frown}{KR}=360°-130°-130° \\~\\ \overset{\frown}{KR}=100°\)
And..
\(m\angle RPK=\frac{\overset{\frown}{KR}+\overset{\frown}{MQ}}{2}\\~\\ m\angle RPK=\frac{100°+28°}{2} \\~\\ m\angle RPK=64°\)
Since \(MR = MK\) and \(\overset{\frown}{MK} = 130°\) , \(\overset{\frown}{MR} = 130°\)
\(\overset{\frown}{MK} +\overset{\frown}{KR} +\overset{\frown}{MR} =360°\)
Replace \(\overset{\frown}{MK}\) with 130° and \(\overset{\frown}{MR}\) with 130°
\(130°+\overset{\frown}{KR}+130°=360° \\~\\ \overset{\frown}{KR}=360°-130°-130° \\~\\ \overset{\frown}{KR}=100°\)
And..
\(m\angle RPK=\frac{\overset{\frown}{KR}+\overset{\frown}{MQ}}{2}\\~\\ m\angle RPK=\frac{100°+28°}{2} \\~\\ m\angle RPK=64°\)
Draw RK
Since minor arc MK = 130°....then angle KRM = (1/2) of this = 65°
But MR = MK...so angle RKM also = 65°
And since minor arc MQ = 28°...then angle QKM = (1/2) of this = 14°
Therefore, angle RKP = m< RKM - m< QKM = 65 - 14 = 51°
Then, in triangle RKP....angle KRP = angle KRM = 65°
And angle RKP = 51°
Therefore, angle RPK = 180 - 65 - 51 = 64°
Rats...!!!...hectictar beat me to it!!!
Her method is better, anyway.....no lines had to be drawn and she just dealt with arc measures....much more efficient.....
Here's one other method to solve this :
Since chord KM = chord RM....then arc KMR = 130 + 130 = 260°
So....minor arc RK = 360 - 260 = 100°
And angle RMK is an inscribed angle subtending this arc...so its measure = 50°
And angle QKM subtends minor arc QM = 28°....so angle QKM = 14°
And by the exterior angle theorem angle RPK = RMK + QKM = 50 + 14 = 64°
[ Note...in essence....this is the same proof as hectictar's ....!!! ]
Hey...here's another way!
∠KRM = 130° / 2 = 65°
∠RKM = 130° / 2 = 65°
∠QKM = 28° / 2 = 14°
∠RKQ = 65° - 14° = 51°
And since there are 180° in triangle KPR.... ∠RPK = 180° - 65° - 51° = 64°
*edit*
Wait a minute...this isn't any different than the second one!!! Ah..sorry about that!