Question

A is an acute angle and `cos A=5/13`. Without using multiplication or calculator,find the value of each of the following trigonometry function a) `cos (180°-A)` b) `sin (180°-A)` c) `tan (180°+A)` ?

Answer 1

We know,that,

`cos(180-A)=-cos A=-5/13`

`sin(180-A)= sin A=sqrt(1-cos^2 A)=12/13`

`tan(180+A)= sin(180+A)/cos(180+A)=(-sin A)/(-cos A)=tan A=12/5`