Evelina

Please help me how to do this: 1) 1 + sina*cosa / (cosa + sina)^2 = 2) sina + cosa / 1- 2sin^2a =

How to do this one? (sina/1-cosa) + (1-cosa/sina) = Also, wanted to ask if I did another one right: 1 - sin^2a + tg^2a * cos^2a = 1 - sin^2a + (sina/cosa)^2 * cos^2a = 1 - sin^2a + sin^2a = 1 ???

I need to prove equality. a) (sina + cosa)^2 -1 / ctga - sinacosa = 2tg^2a b) (sin^2x/sinx-cosx) - (sinx+cosx/tg^2x+1) = sinx + cosx c) sin^4a - sin^2a - cos^4a + cos^2a = cosπ/2 How to do these?

I need to count this: a) 1-tg^2a/1+ctg^2a, when sina =2/3 b) 1-tg^2a/1-ctg^2a, when cosa= -1/3 c) tga * cos^2a, when sina + cosa=5/7 d) tg^2a + 1/sina * 1/cosa + ctg^2a, when tga + ctga =5

How to prove the theorem of sines, using S=(a*b/2) * sin γ ?

I need to prove parallelogram law using the law of cosines. 2AB^2 + 2BC^2 = AC^2 + BD^2 Please, help me to do this.

If (cosa-sina)/sina = 2 , then what is tga = ?

V(CH3OH)= 2 litres ρ(CH3OH) = 0,80 g/ml v(O2) - ? (How much O2 is it needed to burn with 2 litres of CH3OH?)

If √8-a + √5+a = 5, then √(8-a)(5+a) = ... Please help me solve this.

How many solutions equation x^4 + 2x^2 - 15 = 0 has?

oh yes, I wrote the first one wrong. THANK YOU

The b) actually was like this in my book: sin^2x/sinx-cosx - sinx+cosx/tg^2x+1 = sinx + cosx

Well, that‘s what the question says. I can send a picture of it, if you don‘t believe. Show me how you do it with brackets, maybe I‘ll know what to do with that one.

ehh, still don't get it.

Helped alot! Thank you!