A. To find the coterminal angle of -690°, we first minus 360° --> -690° - (-360°) = -330°. The coterminal of -330° is 60°. B. To find the reference angle of 738°, we minus 720° to find the angle: 738° - 720° = 18°.
Coterminal angles are angle whose in standard position and that have a common terminal side. To find the coterminal angle of -690° we could add 360 because it is negative (subtract if positive) so: -690+360 =-330 and -330+360=30° So the smallest positve coterminal angle of -690° is 30°.
Reference angle is the smallest positive acute angle formed by the x-axis and the terminal side. To find the reference angle of 738° we must find first its coterminal angle: 738°-360°=378°-360°=18° Since 18° is acute and positive. Then the reference angle of 738° is 18°.
