# Posts by mtd

Total # Posts: 5

**science**

I believe the noble gas group or Group O. Hopefully someone can verify that. I apologize if that is wrong.

**math**

Take the two equation two unknown down to one unknown by either adding or subtracting the second equation from the first so that one of the uknowns is removed. 2x+y=5 + x-y=1 -------------- 3x=6 x=2 Then plug the newly found x value into one of the equations to find y. In this...

**Math (Trig)**

let me try to type it out again, my apologies. Original problem is--Prove the following: 1- cot^2 x ----------- = cot^2 x tan^2 x - 1 That is how the problem actually looks.

**Math (Trig)**

sorry, another I can't figure out Show that (1-cot^2x)/(tan^2x-1)=cot^2x I started by factoring both as difference of squares. Would I be better served by writing in terms of sine and cosine? Such as: [1-(cos^2x/sin^2x)]/[(sin^2x/cos^2x)-1]=(cos^2x/sin^2x)

**Math (Trigonometry)**

square root(a^2 -u^2) where a>0, let u=(a sinx) where -pi/2<x<pi/2 answer is (a cosx) and I don't know how to get there