Question

Which of the following are lengths of the sides of a 30°-60°-90° triangle? A. 5√3, 15., 10√3 units B. 3, 4, and 5 units C. √3, 3√3 and 2√3 units D. 5√6, 12√6, and 13√6 units​

Answer 1

Answer:

A

Step-by-step explanation:

law of sine

c/sin(C) = b/sin(B) = a/sin(A)

with the sides and corresponding angles being always opposite.

sin(90) = 1

sin(30) = 0.5

c, the Hypotenuse, is the longest side in such a right-angled triangle.

c/1 = b/0.5

b = c×0.5 = c/2

so, one side has to be half the length of the longest side (Hypotenuse).

the only answer meeting that criteria is A.

the longest side is 10×sqrt(3) = 17.32...

the side half of that is 5×sqrt(3).

and Pythagoras for such a triangle is then

c² = (c/2)² + a²

c² = c²/4 + a²

so, a² = 3c²/4

c² = c²/4 + 3c²/4

therefore we can check also the third side

15² = 3×(5×sqrt(3))² = 3×25×3 = 3×75 = 225 = 15²

correct.

A is such a triangle.