Help Proving Trig Identities

I have missedeEvery trig unit ever in school by accident and I just always winged the tests but now I've worked so hard to keep a 90% average (normally i get like a 68% in math) I just don't want it to drop. I have an assignment where I have to complete over 30 questions and get them perfect. I am not asking you to complete the assignment for me but if I post an example of a few could you show me what your doing to get the answer so I can look off that and use it to help me do the rest that would be great. By the way it's proving trig identities.

4.cos^2=sin^2+cos^2-1

15. sin+tan=tan(1+cos)

22.sec^4-tan^4=1+2tan^2

28. sec^2-sin^2=cos^2+tan^2

If you could help i would help me soo much!!

Re: Help Proving Trig Identities

Quote:

Originally Posted by

**vinny2318** I have missedeEvery trig unit ever in school by accident and I just always winged the tests but now I've worked so hard to keep a 90% average (normally i get like a 68% in math)

Don't you have a textbook that you could learn from? If not, there are plenty of websites that you could reference.

Quote:

Originally Posted by

**vinny2318** 4.cos^2=sin^2+cos^2-1

15. sin+tan=tan(1+cos)

22.sec^4-tan^4=1+2tan^2

28. sec^2-sin^2=cos^2+tan^2

None of these make sense. Sine, cosine, and tangent are *functions*. They each require an input. One cannot evaluate "sin" by itself, you need to specify what you are taking the sine of. When you wrote sin^2 Did you mean to write ? Because even then I can't figure out how to interpret that first identity. , for example.

Re: Help Proving Trig Identities

Hello, vinny2318!

This one is not an identity.

Please check for typos.

The left side is: .

. . . . . . . . . .

The left side is: .

. . . . . . . . . .

The left side is: .

. . . . . . . . . .