Answer:
6.55 cm
Explanation:
A triangle is a polygon with three sides and three angles. Types of triangles are isosceles, acute, scalene, obtuse, right and equilateral triangle.
Cosine rule is used to show the relationship between sides and angles of a triangle. If a, b, and c are sides of a triangle, while A, B, and C are angles opposite to the corresponding sides. Then:
c² = a² + b² - 2ab*cos(C)
Given that PR = 13 cm, PQ = 12 cm and angle QPR = 30°, hence:
QR² = PR² + PQ² - 2(PR)(PQ)cos(∠QPR)
QR² = 13² + 12² - 2(13)(12)cos(30) = 169 + 144 - 270
QR² = 43
QR = 6.55 cm