How do you graph theta=(5pi)/4θ=5π4?

1 Answer
Nov 1, 2016

It is the line y = x; x < 0y=x;x<0

Explanation:

This the 3rd quadrant, therefore, we must restrict x and y to be less than 0 , when we substitute tan^-1(y/x)tan1(yx) for thetaθ

tan^-1(y/x) = (5pi)/4; x < 0 and y < 0tan1(yx)=5π4;x<0andy<0

Take the tangent of both sides:

tan(tan^-1(y/x)) = tan((5pi)/4); x < 0 and y < 0tan(tan1(yx))=tan(5π4);x<0andy<0

The tangent "undoes" its inverse and substitute 1 for tan((5pi)/4)tan(5π4):

y/x = 1; x < 0 and y < 0yx=1;x<0andy<0

Multiply both sides by x:

y = x; x < 0y=x;x<0

We dropped the restriction on y, because it is, now, a dependent variable.