Question

DE=EF=20см. знайти DF​

Answer 1

Ответ:Оск DE=EF=20см а DF=DE+EF то DF=20+20=40см

Объяснение:

Answer 2

To find the length of DF, we can use the properties of an isosceles triangle. In an isosceles triangle, the two equal sides are opposite the two equal angles.

Since DE = EF = 20 cm, we know that angle DFE is also equal to angle DEF. Therefore, angle DFE = angle DEF.

Now, let's consider triangle DEF. The sum of the angles in a triangle is always 180 degrees. So, we can write:

angle DEF + angle DFE + angle EFD = 180 degrees.

Since angle DEF = angle DFE, we can rewrite the equation as:

2 * angle DEF + angle EFD = 180 degrees.

Since angle DEF + angle EFD = 180 degrees (from the definition of a straight line), we can substitute this value into the equation:

2 * angle DEF + 180 degrees = 180 degrees.

Subtracting 180 degrees from both sides gives:

2 * angle DEF = 0 degrees.

Dividing both sides by 2 gives:

angle DEF = 0 degrees.

Since angle DEF is 0 degrees, triangle DEF degenerates into a straight line, and the points D, E, and F are collinear.

In this case, the length of DF is simply the sum of the lengths of DE and EF:

DF = DE + EF = 20 cm + 20 cm = 40 cm.

Therefore, the length of DF is 40 cm.