Quadratics and Trigonometry Problems!

[whale95]

Note = [2] means to the power of 2

Q) The equation of the curve is y = 3cos2x. The equation of a line is x+2y=? (pi) . On the same Diagram, sketch the curve and the line for 0<x<? .
Find the first 3 terms in the expansion of (2-x)[2] in ascending power of x.
I did the graph but didnt know how to do the line! :S

Q)2cos? = 1/tan?          0<?<2?
I did upto cos?(2sin?-1)=0
so cos?=0  so 0
and 2sin?-1=0 so ?/6 and 5?/6
so now I have 3 answers which are in bold! how did ?/2 and 3?/2 come??

Q)sinx=3/5 and angle is obtuse. Find tanx and cosx

..........

Identities:
Q) (1+tan[2]?)cos[2]? = 1

Q) sin[2]?/1-cos? = 1+cos?

Q) 1-tan[2]?/1+tan[2]? = 1-2sin[2]?

.........

Q) Find the nature of the root? 2x[2] - ax + 2a[2] = 0

Q) x[2] - 2x + 1 = p(x-3) has equal roots find P??

i did b[2] - 4ac
(-2-p)(-2-p)-4(1)(1+3p) = 0

Thank you in advance!

[~ Miss Relina ~]

your anwsers are here in that link https://studentforums.biz/math-146/c1-doubts-here!!!!!/new/
Mr.Astarmathandphysics anwered them there  : 
they are named  out and out2

post your doubts there and he will answer you so that to avoid confusion