Answer:
see explanation
Step-by-step explanation:
the sum of the 3 angles in the triangle = 180° , then
∠ BAC + 51° + 90° = 180°
∠ BAC + 141° = 180° ( subtract 141° from both sides )
∠ BAC = 39°
using the tangent ratio in the right triangle
tan51° = [tex]\frac{opposite}{adjacent }[/tex] = [tex]\frac{AC}{BC}[/tex] = [tex]\frac{AC}{12.8}[/tex] ( multiply both sides by 12.8 )
12.8 × tan51° = AC , then
AC ≈ 15.8 ( to 1 dec. place )
using the cosine ratio in the right triangle
cos51° = [tex]\frac{adjacent}{hypotenuse}[/tex] = [tex]\frac{BC}{AB}[/tex] = [tex]\frac{12.8}{AB}[/tex] ( multiply both sides by AB )
AB × cos51° = 12.8 ( divide both sides by cos51° )
AB = [tex]\frac{12.8}{cos51}[/tex] ≈ 20.3 ( to 1 dec. place )
