2
$\begingroup$

In the paper I have two lines which have an angle between them (letter C). Also it is told that area of one square is $1 cm^2$. I need to find tangent of the angle C.

What I know is square's side length is 1cm. I tried finding the length of line CB(pythagorean theorem) and drawing the line $AB$.

I know the answer which is $-2.5$

image of the paper

  • 0
    You could use the fact that $\tan(180^{\rm o}-\angle {\rm C})=-\tan(\angle{\rm C})$ – 2017-02-28
  • 0
    Could you explain it a bit wider? By the way, the answer is -2.5. Thanks! – 2017-02-28
  • 0
    Sorry I had been out for a little while, but ATHARVA has perfectly answered your question. – 2017-02-28
  • 0
    Count squares and divide. – 2017-02-28

1 Answers 1

3

produce AC to D. and join BD such that angle CDB forms right angle.

NOW $\tan CDB = \frac{5}{2}$ $ = 2.5$

now $$\tan C = \tan 180-CDB$$ $$ \tan C =-\tan CDB$$ $$ \tan C = -2.5$$