Trig Identities and finding real numbers

I am currently finishing a review of precal for my cal I class. It has been a little while since i have used this kind of math so i am at a stand still. I have five questions.

1. find and equivalent expression involving only sines and cosines, and then simplify it.

sin^2(x) +sin(x)-1+cos^2(x)

2. same as above except:

sec(x) +sin(x)

3.find sec(x) if tan(x)=3/4 and x is in quadrant one.

4. find all real numbers in the interval [0,2pi] that satisfy the equation:

2sin(x)cos(x)+cos(x)=0

5. same as #4 except:

sin(x)=1-2sin^2(x)

I struggled with these kind of problems when i was taking pre-cal. I would greatly appreciate it if someone could help me solve these and teach me a little more about the subject.