prove that the area of an equilateral triangle described on one side of the square is equal to the half the area of the equilateral triangle described on one of its diagonal
Answers
Answer:
let side of first triangle be s
let side of second triangle be S
area of triangle 1÷ by area of triangle 2=. √3/4s^2/
_________________ANSWER_____________
Given: ΔABC and ΔPQC are two equilateral triangle
ΔPQC described on the diagonal PC
And ΔABC described on side AC
PACN is square
To proof : ar(ΔABC) = 1/2ar(ΔPQC)
proof : since ΔABC and ΔPQC are two equilateral triangle. Thus all angles are of 60°
⇒ΔABC ∽ ΔPQC [by AA similarity]
And
In ΔAPC
PC²=AP²+AC² (by Pythagoras theorem)
PC² =AC² +AC² (AP=AC as PACN is square)
PC² =2AC²
PC =√2AC
⇒AC/CP =1/√2
Now,
By area theorem,
ar(ΔABC)/ar(ΔPQC) =AC²/CP²
=(1/√2)²
ar(ΔABC)/ar(ΔPQC) =1/2
⇒2ar(ΔABC ) =ar(ΔPQC)
⇒ar(ΔABC) =1/2ar(PQC)
HENCE PROVED
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