Answer:
44.47 cm² (nearest hundredth)
Step-by-step explanation:
Area of ΔABC = 1/2 x base x height
⇒ 21 = 1/2 x 7 x BC
⇒ BC = 6 cm
Pythagoras' Theorem: a² + b² = c²
(where a and b are the legs, and c is the hypotenuse, of a right triangle)
⇒ AB² + BC² = AC²
⇒ 7² + 6² = AC²
⇒ AC² = 85
⇒ AC = √85 cm
Cosine rule to find length AD:
c² = a² + b² - 2 ab cosC
⇒ DC² = AD² + AC² - 2(AD)(AC)cos(DAC)
⇒ 9.2² = AD² + (√85)² - 2(AD)(√85)cos 73°
⇒ AD² - 5.39106...AD + 0.36 = 0
⇒ AD = 5.323442445, 0.06762541414
⇒ AD = 5.323442445
Area of a triangle ADC: (1/2)absinC
(where a and b are adjacent sides and C is the angle between them)
⇒ area = (1/2) × AC × AD × sin(DAC)
⇒ area = (1/2) × √85 × 5.323442445 × sin(73°)
⇒ area =23.4675821... cm²
Area of quadrilateral = area of ΔABC + area of ΔADC
= 21 + 23.4675821...
= 44.47 cm² (nearest hundredth)
