## Trigonometry (11th Edition) Clone

90$^{\circ}$ is between 1st and 2nd quadrant.
1. This is "if applicable" situation your book is talking about 2. 90$^{\circ}$+360$^{\circ}$=450$^{\circ}$ 90$^{\circ}$-360$^{\circ}$=-270$^{\circ}$ Co-terminal angles always in the same quadrant as original angle.