The length of the side QR in the task content can be determined as; 12.22cm.
What is the length of the third side QR?
It follows from the task content that 2 lengths and one included angle are given in the task content. It therefore follows that the length of side QR can be evaluated by the cosine rule as follows;
QR² = 13² + 4² - (2×4×13×cos70)
QR = √149.4
QR = 12.22cm
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