# Another Maths Question!

https://www.quora.com/profile/Bravewarrior/p-143750744
Here is the question and its solution. I am stuck on part c but I sent the solutions to all parts in case that may be helpful. Can someone please explain part c and its solution? Thank you!
Original post by pigeonwarrior
https://www.quora.com/profile/Bravewarrior/p-143750744
Here is the question and its solution. I am stuck on part c but I sent the solutions to all parts in case that may be helpful. Can someone please explain part c and its solution? Thank you!

What do you understand / think the answer should be. It's based on the two preceding parts.
Original post by mqb2766
What do you understand / think the answer should be. It's based on the two preceding parts.

Ok is it that cos will remain unchanged as if you add on the new restriction to the cos graph, it is still positive as that part of the graph is not in the negative portion/quadrant?
Original post by mqb2766
What do you understand / think the answer should be. It's based on the two preceding parts.

So you would just use the graph to see if with the restriction it is positive or negative?
Original post by pigeonwarrior
So you would just use the graph to see if with the restriction it is positive or negative?

It's really asking about your understanding of arcsin , which has a range -pi/2..pi/2 as the question says (and can be easily inferred from the sin graph) so it's ok in Q1 and Q4. Cos is pos in both those quadrants as you say, so the expression for tan is ok as well.

Note - it would be helpful to use more specific titles for your posts.
(edited 6 months ago)
Original post by mqb2766
It's really asking about your understanding of arcsin , which has a range -pi/2..pi/2 as the question says (and can be easily inferred from the sin graph) so it's ok in Q1 and Q4. Cos is pos in both those quadrants as you say, so the expression for tan is ok as well.

Note - it would be helpful to use more specific titles for your posts.

Thank you! Will keep this in mind for next time 🙂