In △abc, ad and be are the angle bisectors of ∠a and ∠b and de ║ ab . find the length of de if perimeter of abde is 30 cm and ab = 12 cm

DE = 6 cm

Step-by-step explanation:

Let DE = x cm.

Since DE is parallel to AB therefore by the alternate interior angles theorem, m∠BAD = m∠ADE and m∠ABE = m∠DEB ............(1)

As AD is an angle bisector of ∠A, therefore m∠EAD = m∠DAB ; Since BE is an angle bisector of ∠B ⇒ m∠ABE = m∠EBD.

Therefore, from (1) We get ,  m∠EAD = m∠ADE and m∠EBD = m∠BED.

So, the triangles ADE and EDB are then isosceles with AE = ED and ED = DB.

So AE = DE = DB = x, and since the perimeter of ABDE is 30 cm, then

12 + x + x + x = 30

⇒ 12 + 3x = 30

⇒ x = 6

Hence, the length of DE is 6 cm.

DE=6cm

Step-by-step explanation:

Let x=DE, since AB║DE, therefore ∠BAD=∠ADE and ∠ABE=∠BED.        (1)

Also, we are given that AD is the angle bisector of ∠A and BE is the angle bisector of ∠B,

Therefore, ∠EAD=∠DAB and ∠ABE=∠EBD                                             (2)

From (1) and (2), ∠EAD=∠ADE and ∠EBD=∠BED

⇒The ΔADE and ΔEDB then becomes the isosceles triangle with AE=Ed and ED=DB (Sides opposite to equal angles are always equal)

Therefore, AE=DE=DB=x

We are given that the perimeter of ABDE is 30 cm, therefore,

Perimeter of ABDE= sum of all the sides of ABDE

⇒30=AB+BD+DE+AE

⇒30=12+3x

⇒30-12=3x

⇒x=6cm

Therefore, the length of DE= 6cm

x=17

step-by-step explanation:

solve 3x-24=x+10

then that makes it 2x=34 because you subtract an x from both sides to get rid of the one on the right, and then you add 24 to both sides to get rid of the 24 on the left

divide by both sides by 2 to get your answer so that you can get your answer

sorry not sure

step-by-step explanation: