Given an isosceles triangle with length of 2 eq... - JAMB Mathematics 2001 Question
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 option: b
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°
= 2t2 - 3t2 2t2
= -t2/2t2
= -1/2
Thus θ = cos-1 (-0.5) = 120°
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