Answer:
![\theta= cos^(-1)(\frac {N}{mg})](https://img.qammunity.org/2020/formulas/physics/high-school/ivorg6d7p2lxtsqmetjb9lgxpmudpsz6np.png)
Step-by-step explanation:
From the attached sketch where the box represents a car travelling up a hill. The normal force of the car
where m is the mass of the car and g is the gravitational constant
This can be re-written as
![cos\theta= \frac {N}{mg}](https://img.qammunity.org/2020/formulas/physics/high-school/42xosa5x1g7hnzul2lhnya78xxiii23f4h.png)
Getting the inverse of
we have
![\theta= cos^(-1)(\frac {N}{mg})](https://img.qammunity.org/2020/formulas/physics/high-school/ivorg6d7p2lxtsqmetjb9lgxpmudpsz6np.png)
From the diagram also, the ratio of normal force to weight is
![cos\theta](https://img.qammunity.org/2020/formulas/mathematics/college/32ah7t58x8d1s04gj5efr8vn22pxgdirzk.png)
![\frac {mg cos\theta}{mg}=cos\theta](https://img.qammunity.org/2020/formulas/physics/high-school/n8ve7t9v2dqn8r4pmykitjcbh38cqo2ftv.png)
Conclusively,
![\theta= cos^(-1)(\frac {N}{mg})](https://img.qammunity.org/2020/formulas/physics/high-school/ivorg6d7p2lxtsqmetjb9lgxpmudpsz6np.png)