Question

AD is drawn perpendicular to BC, base of an
equilateral triangle ABC. Given BC= 10 cm, find
the length of AD. correct to 1 place of decimal
(ICSE)​

Answer 1

Answer:

Given that in equilateral triangle ABC ,

BC , AB and AC is 10 cm

AD is drawn perpendicular to BC , so D is the median of triangle ABC ,

hence DC =5cm ( half of BC)

In triangle ADC ,

AC is hypotenuse and DC is base and AD perpendicular .

By Pythagoras Theorem ,

H*H =B*B+ P*P

10*10= 5*5 + P*P

100= 25 + P*P

P*P = 100- 25

P*P= 75

P = √75

P = 8.6

Hence AD = 8.6 cm