This is the basic and conceptual question from trigonometric ratios in which we have given a figure of ∆ABC in which ∠B = 90° , ∠A =30° and the length of side AC = 20cm. We have to calculate the length of
(i) BC, (ii) AB.
RS Aggarwal, class 10, chapter 11, question no 20
Draw a right angled △ABC using given instructions:
Here sin30=BC/AC
1/2=BC/20
Or BC=10 cm
By Pythagoras theorem:
(AB)^2=(AB)^2−(BC)^2
=(20)^2−(10)^2
=300
AB=10√3cm.