Question

ABC and ADC are triangles. The area of triangle ADC is 52m^2. Work out the length of AB

Answer 1

Answer:

Tthe length of AB is 13.6 cm

Step-by-step explanation:

Step 1: calculate length CD using the area of a triangle

$A = \frac{1}{2} \times (AD \times CD) \times \ sine (D)\\\\52 = \frac{1}{2} \times (12 \times CD) \times \ sine (102)\\\\52 = 6CD \times 0.978\\\\52 = 5.868CD\\\\CD = \frac{52}{5.868} \\\\CD = 8.862 \ cm$

Step 2: calculate length AC using Cosine rule;

$AC^2 = AD^2 + CD^2 - 2(AD \times CD)cos (D)\\\\AC^2 = 12^2 + 8.862^2 - 2(12 \times 8.862)cos(102)\\\\AC^2 = 222.535 - 2(-22.11)\\\\AC^2 = 222.535 + 44.22\\\\AC^2 = 266.755\\\\AC = \sqrt{266.755} \\\\AC = 16.33 \ cm$

Step 3: Apply sine rule to calculate length AB;

$\frac{AB}{sin \ 46} = \frac{AC}{sin \ 120} \\\\AB = \frac{sin \ 46 \ \ \times \ \ AC}{sin \ 120} \\\\AB = \frac{sin \ 46 \ \ \times \ \ 16.33}{sin \ 120} \\\\AB = 13.56 \ cm \\\\AB = 13.6 \ cm$

Therefore, the length of AB is 13.6 cm