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In a right angle triangle ABC BD is perpendicular to AC. then prove that AB^2-BC^2+AC^2=2*AC*AD

Answer»

tion:GIVEN: In triangle ABC : ANGLE B =90°; BD perpendicular ACTO PROVE: AB²- BC²+ AC² = 2*AC*ADPROOF: In triangle ABC and triangle ADB Angle A = Angle A (common) Angle B = Angle D (90°)( BD perpendicular AC) => Triangle ABC ~ Triangle ADB (A.A) => AB = BC = AC (EQ...1) AD DB AB Similarly, Triangle ABC ~ Triangle BDC => AB = BC = AC (EQ...2) BD DC BC From eq. 1 we have AB = AC AD AB => AB² = AC* AD Similarly from eq. 2 we have BC = AC DC BC => BC²= AC* DCWE KNOW THAT AC² = AC*AC = AC( AD + DC) ( FROM FIGURE) THUS; AB²-BC² + AC² =(AC*AD) - (AC*DC ) +( AC(AD +DC) = AC*AD - AC*DC + AC*AD + AC*DC = AC*AD + AC*AD = 2*AC*AD Hope it helps....



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