 # 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 √𝟓 cm.

We know that \sqrt{5}=\sqrt{2^{2}+1^{2}}

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

Hence, Considering Side 1=2 and Side 2 =1,

We get a right angled triangle such that:

∠𝐴=90°, AB=2cm and AC=1cm Video transcript
"hello students welcome to lido learning today we are going to do the question which is on the screen draw a line segment of length under root 5 centimeter now we know that under root 5 is an irrational number so we cannot use a ruler or a scale to draw a line of this length so what are we going to do we are going to use the pythagoras theorem in mathematics to draw this line so let us see how we can use this theorem so we know that under root of 5 whole square is equal to 2 whole square plus 1 whole square now if you remember the right angle triangle this is the right angle triangle and this is what we can use to draw a length now pythagoras theorem is applicable on a right angle triangle now using this equation we can see that the hypotenuse of any right angle triangle the whole square of it is equal to the sum of the squares of the length and the base of the right angle triangle now using this we can say that's if at all we can create a right angle triangle of this nature then the length this length is going to be the size under root of 5 centimeter so this is how we can do this question and draw a line of under root 5 centimeter if you have any concerns please message below this video and subscribe to this channel thank you"
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