Answer:
d. 6.3
Step-by-step explanation:
Given [tex]b=3,c=9[/tex] and [tex]A=21\degree[/tex], we can use the cosine rule to find [tex]a[/tex].
The cosine rule is given by;
[tex]a^2=b^2+c^2-2bc\cos(A)[/tex]
We substitute the values to obtain;
[tex]a^2=3^2+9^2-2(3)(9)\cos(21\degree)[/tex]
[tex]a^2=9+81-54\cos(21\degree)[/tex]
[tex]a^2=90-50.4133[/tex]
[tex]a^2=39.5867[/tex]
[tex]a=\sqrt{39.5867}[/tex]
[tex]a=6.2918[/tex]
To the nearest tenth, [tex]a=6.3[/tex]
