No 28 itu gimana tolongin dong help

Kelas 10 Matematika
Bab Trigonometri

PR = √(PQ² + QR² - 2 . PQ . QR . cos PQR)
PR = √(4² + 4² - 2 . 4 . 4 . cos 120°)
PR = √(16 + 16 - 32 . (-1/2))
PR = √(32 + 16)
PR = √48 cm

RS/sin RPS = PR/sin PSR
RS = sin 45° . √48 / sin 60°
RS = (1/2 √2 . √48)/(1/2 √3)
RS = √(2 . 48 : 3)
RS = √32
RS = 4√2 cm