# Posts by Evelina

Total # Posts: 17

**math**

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

**math**

Helped alot! Thank you!

**math**

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

**biology**

I have codone AUG. Which one of amino acids will be involved in protein making, if nucleotide with adenine (A) will be changed to nucleotide with cytosine (C)?

**science**

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?)

**chemistry**

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?)

**trig**

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

**trig**

ehh, still don't get it.

**trig**

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.

**trig**

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

**trig**

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

**trig**

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.

**trig**

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

**trig**

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?

**trig**

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 ???

**trig**

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

**trig**

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