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Rachel Erdman
Wiki User
∙ 13y agoTo solve 2 cos2x + sin x - 1 make use of the identity cos2x + sin2x = 1, then:
cos2x = 1 - sin2x
and
2 cos2x + sin x - 1 = 2 (1 - sin2x) + sin x - 1
= 2 - 2 sin2x + sin x - 1
= 1 + sin x - 2 sin2 x
if you let y = sin x, then you can see you have a quadratic:
1 + sin x - 2 sin2 x = 1 + y - 2y2
which can be solved for 1 + y - 2y2 = 0:
1 + y - 2y2 = 0
⇒ 2y2 - y - 1 = 0
⇒ (2y + 1)(y - 1) = 0
⇒ y = -1/2 or 1
but y = sin x, so:
sin x = -1/2 or sin x = 1
and so solve these for x.
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Sin squared theta plus cos squared theta barabar Kya Hota Hai?
1
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Until an "equals" sign shows up somewhere in the expression, there's nothing to prove.
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Sin squared theta plus cos squared theta barabar Kya Hota Hai?
1
If a cos theta plus b sin theta equals 8 and a sin theta - b cos theta equals 5 show that a squared plus b squared equals 89?
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