Let α= ∡ (CBM)= ∡ (PCB)= ∡ (BMA) And β= ∡ (NDC)= ∡ (DCQ)= ∡ (NAD)
Triangle BCP congruent to tri. BAM …( hypoth- leg congruence) And Triangle DAN congruent to tri. DCQ …( hypoth- leg congruence) So AM=CP and AN= CQ S(MAN)= ½. MA.NA.sin(MAN)= ½.MA.NA.sin(90- α- β) S(CPQ)= ½.CP.CQ.sin(PCQ)= ½.CP.CQ.sin(90+ α +β) Note that ∡ (MAN) supplement to ∡ (PCQ) so sin(MAN)= sin(PCQ) =>S(MAN)=S(CPQ)
Is AM and AN perpendicular CP and CQ respectively.Therefore tri. ABM= tri. CBP or tri. AND=tri. CDQ (CP=AM ,CQ=AN, <PCB=<BAM, <DCQ=<NAD ) .But <PCQ +<MAN=180. Therefore (PCQ)/(MAN)=(CP.CQ)/(AM.AN)=1
http://s22.postimg.org/yor6ykls1/pro_1200.png
ReplyDeleteLet α= ∡ (CBM)= ∡ (PCB)= ∡ (BMA)
And β= ∡ (NDC)= ∡ (DCQ)= ∡ (NAD)
Triangle BCP congruent to tri. BAM …( hypoth- leg congruence)
And Triangle DAN congruent to tri. DCQ …( hypoth- leg congruence)
So AM=CP and AN= CQ
S(MAN)= ½. MA.NA.sin(MAN)= ½.MA.NA.sin(90- α- β)
S(CPQ)= ½.CP.CQ.sin(PCQ)= ½.CP.CQ.sin(90+ α +β)
Note that ∡ (MAN) supplement to ∡ (PCQ) so sin(MAN)= sin(PCQ) =>S(MAN)=S(CPQ)
Triangles BCP and ABM are congruent ASA and triangles ADN and CDQ are also congruent ASA.
ReplyDeleteHence <s PCQ and AMN can easily be shown to be supplementary.
So altitudes QX and NY of Tr.s PCQ and AMN respectively are equal since Tr.s QCX and NMY are congruent ASA
So using area = 1/2 base X height
S(CPQ) = S(AMN)
Sumith Peiris
Moratuwa
Sri Lanka
Hi there . Was wondering how you prove that sides ND=DQ and CQ=NA ? You need to prove this to substantiate your congruency theory , or am I incorrect?
DeleteIs AM and AN perpendicular CP and CQ respectively.Therefore tri. ABM= tri. CBP or
ReplyDeletetri. AND=tri. CDQ (CP=AM ,CQ=AN, <PCB=<BAM, <DCQ=<NAD ) .But <PCQ +<MAN=180.
Therefore (PCQ)/(MAN)=(CP.CQ)/(AM.AN)=1