Q7 of 177 Page 23

ABCDE is a pentagon, prove that

Given: ABCDE is a pentagon as shown below


Consider ΔABC and apply triangle law of vector, we get



Similarly, consider ΔADE and apply triangle law of vector, we get



And, consider ΔADC and apply triangle law of vector, we get



Adding (i), (ii) and (iii), we get




Add on both sides we get,




Or


Hence proved.


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