# A maths questionWatch

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#1
Prove that

cosec2X+cot2X=cotX

How to prove it?
0
14 years ago
#2
(Original post by superkillball)
Prove that

cosec2X+cot2X=cotX

How to prove it?
Erm...this is P2 for me from last year....try using the double angle formulae for cosec2x (1/sin2x) and cot2x (1/tan2x)....then see if they cancel to give 1/tanx??

G
0
14 years ago
#3
LHS = cosec2x + cot2x = 1/sin2x + cos2x/sin2x = (1 + cos2x)/sin2x = 2(1 - sin^2x)/2sinxcosx = 2cos^2x/2sinxcosx = cosx/sinx = cotx = RHS.
0
14 years ago
#4
(Original post by Ralfskini)
LHS = cosec2x + cot2x = 1/sin2x + cos2x/sin2x = (1 + cos2x)/sin2x = 2(1 - sin^2x)/2sinxcosx = 2cos^2x/2sinxcosx = cosx/sinx = cotx = RHS.
Yeh...that's what i was thinking....

G
0
#5
thank you
0
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