Question

show that the diagnols of rhombus divide into four congruent triangles

Answer 1

the diagonals of a rhombus are perpendicular to each other so they divide it into 4 triangles

Answer 2

Hello!

Here is your answer!
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Let the rhombus be ABCD and let there diameters intersect each other at O.
Since,in a Rhombus all sides are equal,
Therefore AB=AD
and since ABCD is rhombus therefore its diagonals bisect each other
So,AO=DO
and
AO=AO(common)
Therefore 
ΔABO=~ΔADO
Similarly,ΔABO=~ΔBCO
Similarly,
ΔBCO=~ΔDCO
Therefore 
ΔABO=~ΔBCO=~ΔCDO=~ΔADO
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Hope it helps!