Given an isosceles triangle with length of 2 equal sides t units and opposite side √3t units with angle θ. Find the value of the angle θ opposite to the √3t units.
-
A.
100° -
B.
120° -
C.
30° -
D.
60°
Correct Answer: Option B
Explanation
Cos θ° = t2 + t2 -(√3t)2 2 x t x t
= 2t2 – 3t2 2t2
= -t2/2t2
= -1/2
Thus θ = cos-1 (-0.5) = 120°