EM-1360

Cosine rule

E Math · Secondary 3 · Medium · Cosine rule

In a triangle

PQR

,

PQ=7

cm,

PR=10

cm and

\angle QPR = 60^\circ

. Find the length of

QR

.

$8.89\text{ cm (to 3 s.f.)}$
$5.48\text{ cm}$
$13.2\text{ cm}$
$79\text{ cm}$

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