Question

Cot²3x - 3cot3x +2 = 0
cotx = t
what equation for t

Answer 1

Explanation:

cot²(3x)=y

y²-3y+2=0

y²-y-2y+2=0

y(y-1)-2(y-1)=0

(y-1)(y-2)=0

y=1,y=2

cot3x=1

tan 3x=1=tan (π/4)=tan (nπ+π/4)

3x=nπ+π/4=(4nπ+π)/4=(4n+1)π/4

x=(4nπ+1)π/12,n is an integer.

cot 3x=2

tan 3x=1/2

3x=tan^{-1}(1/2)≈26.57°+360n

x≈8.86°+120n