Question

Is the function sec t positive or negative in Quadrant II?

Answer 1

sec(t) = 1/cos(t). So sec(t) is the same sign with cos(t)

In quadrant II, cos(t) is negative. So is sec(t)

Answer 2

Oh, so it's negative? Thank you for actually explaining that. :)

Answer 3

What about this one @linh412986 ? Determine the sign of sin 5pi/4 without using a calculator.

Answer 4

\[\frac{ 5\pi }{ 4 }\]

Answer 5

\[\sin (5\pi/4) = \sin(\pi + \pi/4)\] From this unit circle, we can see \[\sin(\pi + \pi/4) = -\sin(\pi/4) = - \frac{ \sqrt{2} }{ 2 }\]

Answer 6

How did you know that sin(5pi/4) was equal to sin(pi+pi/4)?

Answer 7

radian measurements i believe

Answer 8

WHAT ?? It is so clearly :)) 5/4 = 1 + 1/4 :))

Answer 9

How on earth? I'm so confused by this lesson.. So 1+1=5?

Answer 10

OMG! I see what you did! You did an uneven fraction. I'm such an idiot. -_-

Answer 11

Ah, no no :) \[\frac{ 5 }{ 4 } = 1 + \frac{ 1 }{ 4 }\] Is it clear for you :)

Answer 12

I feel... so dumb.

Answer 13

You welcome

Answer 14

Wait, so after you get\[\pi + \frac{ \pi }{ 4 } \] ...How did you turn that into:\[-\sin (\frac{ \pi }{ 4 })\]???

Answer 15

See this unit circle, you should learn again of a unit circle. Axis of sine is y axis, if an angle is added by Pi, then we have a sine value is negative. Is it clear?

Answer 16

Yes, I think so. Much better. Thank you so much! God bless you! :p Sorry I'm so slow. I'm homeschooled, so I am teaching myself all of this, and it's really hard to do that. :c

Answer 17

No problem, I also learn by myself. Google is my teacher

Answer 18

Haha. :) Awesome.