Answer:
The length of QR is 29.9 cm
Step-by-step explanation:
Let us revise the sine and cosine rules
In triangle ABC:
[tex]\frac{AB}{sin(C)}=\frac{BC}{sin(A)}=\frac{AC}{sin(B)}[/tex] ⇒ sine rule
(AC)² = (AB)² + (BC)² - 2(AB)(BC)cos(∠B) ⇒ cosine rule
Let us use these rules to solve the question
In Δ PQS
∵ [tex]\frac{PS}{sin(Q)}=\frac{QS}{sin(P)}[/tex]
∵ PS = 11.7 cm
∵ m∠P = 95°, m∠Q = 28°
→ Substitute them in the rule above
∴ [tex]\frac{11.7}{sin(28)}=\frac{QS}{sin(95)}[/tex]
→ By using cross multiplication
∴ QS × sin(28) = 11.7 × sin(95)
→ Divide both sides by sin(28) to find QS
∴ QS = 24.82680292 cm
Now let us use the cosine rule to find QR
In Δ QSR
∵ (QR)² = (QS)² + (RS)² - 2(QS)(RS)cos(∠QSR)
∵ RS = 10.2 cm
∵ m∠QSR = 110°
→ Substitute these values in the rule above
∴ (QR)² = (24.82680292)² + (10.2)² - 2(24.82680292)(10.2)cos(110)
∴ (QR)² = 893.631984
→ Take √ for both sides
∴ QR = 29.89367799
→ Round it to 3 significant figures
∴ QR = 29.9 cm
