In isosceles ∆ABC the segment BD (with D ∈ AC ) is the median to the base AC . Find BD, if the perimeter of ∆ABC is 50m, and the perimeter of ∆ABD is 40m.

Respuesta :

Given:

(Isosceles Trianlge) ----∆ABC Perimeter = 50 meters 
(Right Triangle) ---------∆ABD Perimeter = 40 meters
Segment BD bisects segment AC into two equal lenghts

Required: BD

Solution: 

We know that isosceles triangle has two equal legs and a base. Therefore,
For 
∆ABC,
AB & BC are the two equal legs.
AC is the base.

For right triangle ∆ABD,
AB is the hypotenuse
AD is the base leg
BD is the other leg


Let us represent segments AB & BC as a
                           segment  AC as b
                           segment BD as h        
                           segment AD as b/2 

In equation we have,
 ∆ABC Perimeter = a + a + b
                       50 = 2a + b                   eq. (1)

∆ABD Perimeter = a + b/2 + h
                       40 = a + b/2 + h            eq. (2)

Dividing eq. (1) by 2, we get
                       25 = a + b/2                  eq. (3)

Substitute eq. (3) in eq. (2),
                        40 = (25) + h
                         h = 15 meters

 ANSWER: BD = 15 meters

The length of the height triangle ABC is BD i.e., [tex]15\;units[/tex].

According to the question, In isosceles [tex]∆ABC[/tex]  the segment BD is the median to the base AC . Also, the perimeter of ∆ABC is 50m, and the perimeter of the triangle [tex]ABD[/tex] is 40m.

Let the length of the equal sides of the isosceles triangle be [tex]x \;meters[/tex] and the length of the base of the isosceles triangle is [tex]2y\;meters[/tex].

[tex]Perimeter_{ABC}=x+x+2y\\2x+2y=50\\x+y=25\\x=25-y----(i)[/tex]

Also,

[tex]Perimeter_{ABD}=x+y+BD\\x+y+\sqrt{x^2-y^2}=40\\x+y+\sqrt{(25-y)^2-y^2}=40\\25+\sqrt{625-50y}=40\\\sqrt{625-50y}=15\\625-50y=225\\y=8\;units[/tex]

So,

[tex]x=25-8\\x=17\;units[/tex]

Now,

[tex]BD=40-x-y\\BD=40-17-8\\BD=15\;units[/tex]

Hence, the length of the height triangle ABC is BD i.e., [tex]15\;units[/tex].

Learn more about isosceles triangles here:

https://brainly.com/question/7830547?referrer=searchResults

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