Question: Practice 2
Fill in the blanks.
(1) Between $-360^\circ$ and $720^\circ$, the angles that have the same terminal side as $1050^\circ$ are ______ .
(2) The smallest positive angle that has the same terminal side as $1840^\circ$ is ______ .
(3) The smallest positive angle that has the same terminal side as $-1840^\circ$ is ______ .
1. **State the problem:** Find angles with the same terminal side as given angles within specified ranges.
2. **Recall the formula:** Angles that differ by multiples of $360^\circ$ have the same terminal side.
3. **For (1):** Find all angles $\theta$ such that $\theta = 1050^\circ - 360^\circ k$ for integers $k$, and $-360^\circ \leq \theta \leq 720^\circ$.
4. Calculate:
- For $k=2$: $1050^\circ - 360^\circ \times 2 = 1050^\circ - 720^\circ = 330^\circ$ (within range)
- For $k=3$: $1050^\circ - 1080^\circ = -30^\circ$ (within range)
- For $k=1$: $1050^\circ - 360^\circ = 690^\circ$ (within range)
- For $k=0$: $1050^\circ$ (not in range, since $1050^\circ > 720^\circ$)
- For $k=4$: $1050^\circ - 1440^\circ = -390^\circ$ (less than $-360^\circ$, exclude)
So the angles are $-30^\circ$, $330^\circ$, and $690^\circ$.
5. **For (2):** Find the smallest positive angle coterminal with $1840^\circ$.
Calculate $1840^\circ \mod 360^\circ$:
$$1840^\circ - 360^\circ \times \left\lfloor \frac{1840}{360} \right\rfloor = 1840^\circ - 360^\circ \times 5 = 1840^\circ - 1800^\circ = 40^\circ$$
So the smallest positive angle is $40^\circ$.
6. **For (3):** Find the smallest positive angle coterminal with $-1840^\circ$.
Calculate $-1840^\circ \mod 360^\circ$:
Add $360^\circ$ multiples until positive:
$$-1840^\circ + 360^\circ \times 6 = -1840^\circ + 2160^\circ = 320^\circ$$
So the smallest positive angle is $320^\circ$.
**Final answers:**
(1) $-30^\circ$, $330^\circ$, $690^\circ$
(2) $40^\circ$
(3) $320^\circ$