Given triangle is a right angle triangle so we are allowed to use trigonometric formulas.
We want to find Hypotenuse using angle A and base 7 cm
so right choice is to use cosine
[tex] \cos(A)=\frac{AC}{AB} [/tex]
[tex] \cos(25^{\circ})=\frac{7}{AB} [/tex]
[tex] 0.90631=\frac{7}{AB} [/tex]
[tex] AB=\frac{7}{0.90631} [/tex]
[tex] AB=7.72362657369 [/tex]
Hence value of side AB is approx 7.72 cm.
