Sunday, 11 March 2018

How to decide dimensions of cyclic quadrilateral?

Circle with center O   PQ = a QR=b RS=c SP=d              
Radius of circle R 5     Sin R Sin theta Cos R Cos theta Height of isosceles triangle Angle between Radius & side    
Angle bet P & Q    60 30 0.523599 0.5 2.5 0.866025 4.330127 4.330127019 60 Angle OPQ  
Angle bet Q & R   120 60 1.047198 0.866025404 4.330127 0.5 2.5 2.5 30 Angle OQR  
Angle bet R & S   90 45 0.785398 0.707106781 3.5355339 0.707107 3.535534 3.535533906 45 Angle ORS  
Angle bet S & P   90 45 0.785398 0.707106781 3.5355339 0.707107 3.535534 3.535533906 45 Angle OSP  
                         
PQ   5                    
QR   8.660254                    
RS   7.071068                    
SP   7.071068                    
                         
                         
Area of Triangle OPQ   10.82532 10.825                  
Area of Triangle OQR   10.82532                    
Area of Triangle OPQ   12.5                    
Area of Triangle OPQ   12.5                    
Are of Quad PQRS   46.65064                    
                         
Angle bet PQ & QR   90                    
Angle bet QR & RS   75                    
Angle bet RS & SP   90                    
Angle bet SP & PQ   105                    
Angle Q + Angle S   180 Because it is a cyclic quadrilateral                  
Angle P + Angle R   180 Because it is a cyclic quadrilateral                  
Sum ofangles of quad.   360       rcumfewrence            
                         
Circumference   31.41593                    
Perimeter of quad   27.80239 It is always less than circumference of the circle in which it is inscribed                  
                         
Diagonal PR         Sin R Sin Theta            
Angle bet P and R Angle OPQ + Angle OQR 180 90 1.570796 1 5            
  (1/2PR)/R= Sin (1/2*Angle OPR)                      
Diagonal PR = 10                      
                         
Diagonal QS         Sin R Sin             
Angle bet Q and S Angle OQR + Angle ORS 210 105 1.832596 0.965925826 4.8296291            
  (1/2QS)/R= Sin (1/2*Angle OQS)                      
Diagonal QS = 9.659258263                      
                         
Let E bepoint of intersection of the diagonals                        
PE/ER= da /cb 0.577350269     By Similarity of triagles                 
PR/ER = 1.577350269                      
ER =  6.339745962                      
PE = PR-ER 3.660254038                      
                         
SE/EQ= cd/ba 1.154700538                      
SQ/EQ= 2.154700538                      
EQ= 4.482877361                      
SE=SQ-EQ 5.176380902                      
                         
PE*ER= 23.20508076                      
SE*EQ= 23.20508076                      
                         
Internal intersecting chord property proved.                        

In a cyclic quadrilateral, given 3 sides and included angle between two of these sides, how to find fourth side?

Given 3 sides and angle included between 2 sides how to find fourth side of cyclic quadrilateral
PQ=a 2
QR=b 3    Radians Cos Sin
Angle PQR 135 2.356194 -0.70711 0.707107
RS=c 4 RS can not be greater than 2R
Find PR by cosine rule 21.48528 4.635222
2R = PR / Sin (angle PQR) 6.555194 So R= 3.277597
Find angle ROS by (1/2*RS)/R= Sin (1/2*Angle ROS) 0.610203 0.656317 37.6042 0.656317 0.792245 0.610203
1/2*Angle ROS=Angle RPS 37.6042
AngleRSP= 180 deg- Angle PQR (Reason- Oppo. Angle of cyclic quad. Are supplementary 45 82.6042 97.3958 97.3958
Find angle SRP by anglesum property of triangle 97.3958 1.699877 0.991681
Angle SOR = 2 x Angle SRP
1/2*SP/R= Sin(Angle SRP)
Thus SP can be found, in otherwordsSP can befoundby Sine Rule SP= 6.500658
Remember the constant of sine rule is 2xR