1. **State the problem:** We need to find which of the given trigonometric expressions equal 1. 2. **Recall the values of basic trigonometric functions at special angles:** - $\sin 0^\circ = 0$ - $\cos 0^\circ = 1$ - $\tan 0^\circ = 0$ - $\cos 45^\circ = \frac{\sqrt{2}}{2} \approx 0.707$ - $\sin 90^\circ = 1$ - $\cos 90^\circ = 0$ - $\tan 90^\circ$ is undefined (tends to infinity) - $\tan 45^\circ = 1$ 3. **Evaluate each option:** - A. $\sin 0^\circ = 0 \neq 1$ - B. $\cos 0^\circ = 1$ - C. $\tan 0^\circ = 0 \neq 1$ - D. $\cos 45^\circ = \frac{\sqrt{2}}{2} \neq 1$ - E. $\sin 90^\circ = 1$ - F. $\cos 90^\circ = 0 \neq 1$ - G. $\tan 90^\circ$ undefined, so not equal to 1 - H. $\tan 45^\circ = 1$ 4. **Final answer:** The options with value 1 are B, E, and H.