You have to make the base of 4 cm with scale and make 90° on one of its end and then cut its  height take it by P.T. and join it

first take the base as 4 cm long and place the needle of the compass on the left, point and make a 90 degree angle, now open the compass 9 cm long and by placing the needle on the right point of the base cut an arc on the 90 degree angle. Join all the points and label the figue. I have also attached a picture which will help you.
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your welcome
it wasn't for u !
oh sorry! but the notification came to me so I was mistakened!
sorry! I'm totally getting confused what's happening!
no need of sorry akankshaprjpt, the appreciation was for u not for 1st