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What is the area of triangle ABC?

Select the correct choice.

A: 6sqrt3
B: 18sqrt3
C: 36sqrt3
D: 72sqrt3

What is the area of triangle ABC Select the correct choice A 6sqrt3 B 18sqrt3 C 36sqrt3 D 72sqrt3 class=

Respuesta :

Answer:

C

Step-by-step explanation:

The area (A) of the triangle is calculated as

A = [tex]\frac{1}{2}[/tex] bh ( b is the base and h the perpendicular height )

The triangle is equilateral , since 3 angles = 60°

Then base AB = 12

Find height CD using the sine ratio in the right triangle ( there are 2 )

sin60° = [tex]\frac{opposite}{hypotenuse}[/tex] = [tex]\frac{CD}{BC}[/tex] = [tex]\frac{CD}{12}[/tex] = [tex]\frac{\sqrt{3} }{2}[/tex] ← exact value of sin60° ( cross- multiply )

2CD = 12[tex]\sqrt{3}[/tex] ( divide both sides by 2 )

CD = 6[tex]\sqrt{3}[/tex]

Then

A = [tex]\frac{1}{2}[/tex] × 12 × 6[tex]\sqrt{3}[/tex] = 6 × 6[tex]\sqrt{3}[/tex] = 36[tex]\sqrt{3}[/tex] units² → C