express each value as a trigonometric function of an angle in Quadrant I??

1. sin 390

2. sec(-1290)

thank you !!!!!

Guest May 17, 2018

#1**+1 **

It is always the acute angle from the x axis that counts.

so you either use 180 or 360

1. sin 390

one complete revolution and 30 degrees more. That is just sin 30

2. sec(-1290)

1390/360 = 139/36 = 3 clockwise revolutions -210

-210 is equivalent to 360-210 = 150 which is in the second quad

180-150=30

sec = 1/cos and cos is negative in the second quad so so is sec

sec(-1290)= - sec(30)

Melody
May 17, 2018