The trigonometric function gives the ratio of different sides of a right-angle triangle. The length of the base of the isosceles triangle is 21.19 units.
What are Trigonometric functions?
The trigonometric function gives the ratio of different sides of a right-angle triangle.
[tex]\rm Sin \theta=\dfrac{Perpendicular}{Hypotenuse}\\\\\\Cos \theta=\dfrac{Base}{Hypotenuse}\\\\\\Tan \theta=\dfrac{Perpendicular}{Base}[/tex]
where perpendicular is the side of the triangle which is opposite to the angle, and the hypotenuse is the longest side of the triangle which is opposite to the 90° angle.
In order to solve the problem, we will draw a line between the triangle such that it will bisect the angle at the top(∠A) and the base(BC). As shown in the image below.
Now, as we know that the line(AD) is perpendicular to the base(BC) of the isosceles triangle, therefore, using the function of trigonometry in the Δ ABD we can write,
[tex]Cos \theta=\dfrac{BD}{AB}\\\\\\Cos (\angle B)=\dfrac{BD}{12}\\\\\\Cos 28^o \times 12={BD}\\\\BD = 10.5953[/tex]
Now, we know that the line BD divides the base BC into two equal parts, therefore, BD=BC.
BC = BD + DC
BC = 10.5953 +10.5953
BC = 21.19 units
Hence, the length of the base of the isosceles triangle is21.19 units.
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