Suppose an isosceles triangle has two sides of length 42 and 35, and that the angle between these two sides is 120 degree. what

Question

n200080 [17]

4 years ago

12

Suppose an isosceles triangle has two sides of length 42 and 35, and that the angle between these two sides is 120 degree. what

is the length of the third side of the triangle? a. 43.65 b.77 c.58.04 d.66.78

Mathematics

1 answer:

Citrus2011 [14] · Answer 1 · 2021-11-16T20:52:51+03:00

Citrus2011 [14]4 years ago

3 0

Suppose that a=42, b=35, c is unknown, and C = 120°

$c^2 = a^2 + b^2 -2ab(cosC)$

$c^2 = 42^2 + 35^2 -(2*42*35*cos120)

(cos120=-0.5)

c^2 = 1764 + 1225 -(2940*cos120)

c^2 = 2989 -(2940*-0.5)

c^2 = 2989+1470

c^2=4459

c= \sqrt{c^2} 

c=\sqrt{4459}$