 # Selina Solutions Class 9 Mathematics Solutions for Exercise 1(D) in Chapter 1 - Chapter 1- Rational and Irrational Numbers

Draw a line segment of length √𝟖 cm.

We know that, \sqrt{8}=\sqrt{3^{2}-1^{2}}

Which relates to: Hypotenuse= \sqrt{\operatorname{side} 1^{2}+\operatorname{side} 2^{2}}[\text { Pythagoras theorem }]

Hypotenuse²-Side1² = Side2²

Hence, Considering Hypotenuse =3cm and Side 1 =1 cm,

We get a right angled triangle OAB such that:

∠A=90°, OB=3cm and AB=1cm Video transcript
"hello everyone welcome to lido learning so we've got a question on the screen draw a line segment of length under root eight centimeter now if you see under root eight is an irrational number so drawing an irrational number the length with the length of under root eight centimeter is not easy it doesn't seem easy it is easy how we are going to solve it is we first understand the concept through a right angle triangle so this is the right angle triangle and if you see the angle this is a 90 degree angle let's name it oh another vertex says a and the other other vertex as d now in this right angled triangle we can have the length as eight and one and three so you can understand from this concept that under root eight can be written as under root of 3 square minus 1 square and with this information and the right angle triangle that we could create using the pythagoras theorem you can say that the hypotenuse whole square is equal to base whole square plus length whole square so we can easily relate it with hypotenuse whole square is 3 square base whole square is under root of 8 whole square and length is 1 whole square so if we can draw a right angle triangle of this form so we can get the length of under root 8 as ao so we can draw this length of under root eight centimeter which is mentioned in the question through a right angle triangle and therefore ao is equal to under root eight which can be drawn on a piece of paper using the right angle triangle so friends if you have any concerns please write down below this video and subscribe to the channel thank you "
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