EM-1369

Cosine rule

E Math · Secondary 3 · Medium · Cosine rule

In triangle PQR,

PQ = 9\text{ cm}

,

PR = 13\text{ cm}

and angle

QPR = 48^\circ

. Using the cosine rule, find the length of side

QR

.

$9.7\text{ cm}$
$6.3\text{ cm}$
$15.3\text{ cm}$
$22.0\text{ cm}$

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