EM-1365

Cosine rule

E Math · Secondary 3 · Medium · Cosine rule

Triangle PQR has sides

PQ = 9\text{ cm}

,

PR = 11\text{ cm}

and included angle

\angle QPR = 58^\circ

. Using the cosine rule, find the length of side

QR

.

7.3 cm
8.9 cm
9.9 cm
10.8 cm

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