Answer
given,
[tex]F_L= 1.52\ N[/tex]
[tex]\theta_L= 31^0[/tex]
mass of book = 0.305 Kg
so, from the diagram attached below
[tex]F_L cos {\theta_L} + F_b sin {\theta_b} = m g[/tex]
[tex]1.52 times cos {31^0} + F_b sin {\theta_b} = 0.305 \times 9.8[/tex]
[tex] F_b sin {\theta_b} = 2.989 -1.303[/tex]
[tex] F_b sin {\theta_b} = 1.686[/tex]
computing horizontal component
[tex] F_b cos {\theta_b} = F_L sin {\theta_L}[/tex]
[tex]cos {\theta_b} = \dfrac{F_L sin {\theta_L}}{F_b}[/tex]
[tex]cos {\theta_b} = \dfrac{1.52 \times sin {31^0}}{1.686}[/tex]
[tex]cos {\theta_b} = 0.464[/tex]
θ = 62.35°