In triangle PQR, PQ = 1cm, QR = 2cm and PQR..

Question 1 Report

In triangle PQR, PQ = 1cm, QR = 2cm and PQR = 120o Find the longest side of the triangle

\sqrt{3}

\sqrt{7}

3cm

7cm

Answer Details

PR2 = PQ2 + QR2 - 2(QR)(PQ) COS 120o
PR2 = 12 + 22 - 2(1)(2) x - cos 60o
= 5 - 2(1)(2) x - $\frac{1}{2}$
= 5 + 2 = 7
PR = $\sqrt{7}$ cm