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Question from Brian, a student:

I need help proving:

1-tan^3t/1-tant=sec^2t+tant

Brian,

The pattern you need to recognize here is the difference of cubes expression

x3 - y3 = (x - y)(x2 + xy + y2)

In your problem I see this with x = 1 and y = tan(t).

Start with the left side of your expression and multiply the numerator and denominator by (1 + tan(t) + tan2(t)). Use the difference of cubes expression to simplify.

I hope this helps,
Harley

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