# Trigonometric proof

Thread starter 4 years ago
#1
Prove that 2sinxcosx/tanx = 2-2sin^2(x)
0
4 years ago
#2
(Original post by gcsemusicsucks)
Hope it helps!
Please don't post full solutions.
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4 years ago
#3
(Original post by Mr M)
Please don't post full solutions.

It's considered poor form to work on both sides of an identity at the same time. Start on one side and work towards the other.
Sorry! And I don't think I worked on both sides at the same time? I worked from the LHS
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4 years ago
#4
(Original post by gcsemusicsucks)
Sorry! And I don't think I worked on both sides at the same time? I worked from the LHS
You didn't - it was my mistake, my head doesn't rotate 90 degrees very easily.
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4 years ago
#5
(Original post by gcsemusicsucks)
Sorry! And I don't think I worked on both sides at the same time? I worked from the LHS
Could you edit and remove your solution and just give a hint
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4 years ago
#6
(Original post by olympiad1357)
Prove that 2sinxcosx/tanx = 2-2sin^2(x)
Division by tan is the same as multiplication by cot. Also consider using Pythagoras' identity.
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4 years ago
#7
(Original post by olympiad1357)
Prove that 2sinxcosx/tanx = 2-2sin^2(x)
Could you perhaps use any trigonometric identities to help you move in the right direction?
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4 years ago
#8
(Original post by Desmos)
Division by tan is the same as multiplication by cot. Also consider using Pythagoras' identity.
I think talking about cot would be overcomplicating things. But yes Pythagoras' identity would be useful.
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