Prove the following trigonometric identity \(\displaystyle{\frac{{{\tan{{\left({\frac{{\pi}}{{{4}}}}+{x}\right)}}}-{\tan{{\left({\frac{{\pi}}{{{4}}}}-{x}\right)}}}}}{{{\tan{{\left({\frac{{\pi}}{{{4}}}}+{x}\right)}}}+{\tan{{\left({\frac{{\pi}}{{{4}}}}-{x}\right)}}}}}}={2}{\sin{{x}}}{\cos{{x}}}\)

Tony Mccarthy

Tony Mccarthy

Answered question

2022-03-29

Prove the following trigonometric identity
tan(π4+x)tan(π4x)tan(π4+x)+tan(π4x)=2sinxcosx

Answer & Explanation

German Ferguson

German Ferguson

Beginner2022-03-30Added 18 answers

multiplying the top and bottom by cos(π4x)cos(π4+x) gives you
tan(π4+x)tan(π4x)tan(π4+x)+tan(π4x)
=sin(π4+x)cos(π4x)sin(π4x)cos(π4+x)sin(π4+x)cos(π4x)+sin(π4x)cos(π4+x)
=sin(π4+xπ4x)sin(π4+x+π4x)
=sin2x
=2sinxcosx

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