Melody

\theta= \tan^{-1}{(\frac{\Delta{y}}{\Delta{x}})} =

$$\theta= \tan^{-1}{(\frac{\Delta{y}}{\Delta{x}})} =$$

By Heureka.

Thank you anonymous for you good manners. 

Thanks anonymous.

I assume you just want to expand and then simplify this.

(x+7)(x+9)

=x(x+9)+7(x+9)

=x²+9x+7x+63

=x²+16x+63

 x² + 7x + 19 

$$If \qquad x^2+7x+19=0 \mbox{ which it doesn't - then}\\\\
x=\frac{-7\pm \sqrt{49-76}}{2}\\\\
x=\frac{-7\pm(\sqrt{17})i}{2}\\\\$$

SO

$$x^2+7x+19=\left(x+\frac{7+(\sqrt{17})i}{2}\right)
\left(x+\frac{7-(\sqrt{17})i}{2}\right)$$

I think that is ok.

You are ofcourse correct Bertie.  Thank you.

I gave myself -3 for my lack of diligence!  That'll teach me - maybe???  

Thanks Alan,

I didn't think Chris's was wrong.  Your's is neater though!   

Chris might think i can't have his points but I've still got his sunnies!!!   And, he can't have them back. 

I've already lost the working for this once.  But I will try again.

$$tan(2A)\\\\$$

$$=\frac{sin(2A)}{Cos(2A)}\\\\$$

$$=\frac{2sinAcosA}{Cos^2A-Sin^2A}\\\\$$

$$=\dfrac{\frac{2sinAcosA}{Cos^2A}}{\frac{Cos^2A-Sin^2A}{Cos^2A}}\\\\$$

$$=\dfrac{2tanA}{1-tan^2A}\\\\$$

There you go!

Tuesday 20/5/14

Forum Interest Question - Web2.ocalculator

Thank you admin,

That will be wonderful.