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Simplify the following. sin3A−cos3AsinA−cosA \frac{sin³A - cos^3 A}{sin A - cos A} sinA−cosAsin3A−cos3A​​where A is an acute angle.
Question

Simplify the following. sin3Acos3AsinAcosA \frac{sin³A - cos^3 A}{sin A - cos A} ​where A is an acute angle.

A.

1 + sinA cosA

B.

1 – 3 sinA

C.

3 cosA - 1

D.

sinA + cosA

Correct option is A

Given:

sin3Acos3AsinAcosA\frac {sin^3 A- cos^3A}{sinA-cosA}​​

Formula Used:

sin2A+cos2A=1sin^2A+cos^2A = 1​​

Solution:

=sin3Acos3AsinAcosA =(sinAcosA)(sin2A+cos2A+sinAcosA)(sinAcosA) =sin2A+cos2A+sinAcosA =1+sinAcosA=\frac {sin^3A-cos^3A}{sinA-cosA}\\ \ \\ = \frac{\cancel{ (\sin A - \cos A)}(\sin^2 A + \cos^2 A +\sin A \cdot \cos A)}{\cancel{(\sin A -\cos A)}} \\ \ \\ = \sin^2 A + \cos^2 A +\sin A \cdot \cos A \\ \ \\ = 1+sin A \cdot \cos A ​​

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