a) To determine the other angles of △ABC, we will use the Sine Rule.
Step 1: Apply the Sine Rule to find angle C^.
The Sine Rule states that for a triangle with sides a,b,c and opposite angles A^,B^,C^:
sinA^a=sinB^b=sinC^c
Given A^=40∘, BC=12 (side a), and AB=15 (side c). We want to find C^.
sinA^BC=sinC^AB
sin40∘12=sinC^15
sinC^=1215sin40∘
sinC^=1215×0.6427876
sinC^≈0.8034845
Since C^ is acute, we take the principal value:
C^=arcsin(0.8034845)
C^≈53.46∘
Step 2: Find angle B^ using the sum of angles in a triangle.
The sum of angles in a triangle is 180∘.
A^+B^+C^=180∘
40∘+B^+53.46∘=180∘
B^=180∘−40∘−53.46∘
B^=180∘−93.46∘
B^≈86.54∘
The other angles of the triangle are C^≈53.46∘,B^≈86.54∘.
b) To calculate the lengths of the sides of △PQR, we will first find the missing angle and then use the Sine Rule.
Step 1: Find angle P^ using the sum of angles in a triangle.
Given Q^=110∘ and R^=40∘.
P^+Q^+R^=180∘
P^+110∘+40∘=180∘
P^=180∘−110∘−40∘
P^=180∘−150∘
P^=30∘
Step 2: Apply the Sine Rule to find side QR.
Given PQ=13. We want to find QR (opposite P^) and PR (opposite Q^).
sinR^PQ=sinP^QR
sin40∘13=sin30∘QR
QR=sin40∘13sin30∘
QR=0.642787613×0.5
QR=0.64278766.5
QR≈10.12
Step 3: Apply the Sine Rule to find side PR.
sinR^PQ=sinQ^PR
sin40∘13=sin110∘PR
PR=sin40∘13sin110∘
PR=0.642787613×0.9396926
PR=0.642787612.2160038
PR≈19.00
The lengths of the sides are QR≈10.12,PR≈19.00.
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