thisgirl0709
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Use the properties of sine and cosine to express in terms of tan x: tan(90 degrees -x)
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Sammylou40
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There’s me thinking we were going to discuss the pros and cons of a lovely summer glow.....
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Maximus 190
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Use the trigonometric identity tanx = sinx/cosx

Then how can you express sin(90-x) and cos(90-x) in terms of just cos(x) or sin(x)? Think about translations. sin(90-x), or sin(-x+90) is equal to a flip along the x axis and shifted left by 90° of sin(x), what does that now look like?
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Sammylou40
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(Original post by Maximus 190)
Use the trigonometric identity tanx = sinx/cosx

Then how can you express sin(90-x) and cos(90-x) in terms of just cos(x) or sin(x)? Think about translations. sin(90-x), or sin(-x+90) is equal to a flip along the x axis and shifted left by 90° of sin(x), what does that now look like?
I prefer my version.....
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simon0
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Other ways include:

1) Perform the transformation of: tan(90 - x), compared to: tan(x).
Then see it resembles a particular trigonometric function which has a definition in terms of sin and cos.

2) Note:  \tan (x) = \dfrac{ \sin(x) }{ \cos(x) }.

Then use the formulas for:  \sin (a-b), \, \cos (a - b).
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