1. ## trig special rations

hi guys! i need explanation

how do we solve questions like sin 135, cos 60, tan -180, cos -270 without using calculator.
Pls explain it to me clearly. thank u

2. Originally Posted by thereddemon
hi guys! i need explanation

how do we solve questions like sin 135, cos 60, tan -180, cos -270 without using calculator.
Pls explain it to me clearly. thank u
First of all you should remember the basic sine and cosine values:
$\displaystyle sin(30)=\frac{1}{2}$ , $\displaystyle cos(30)=\frac{\sqrt{3}}{2}$

$\displaystyle sin(45)=\frac{\sqrt{2}}{2}$ ,$\displaystyle cos(45)=\frac{\sqrt{2}}{2}$

$\displaystyle sin(60)=\frac{\sqrt{3}}{2}$ ,$\displaystyle cos(60)=\frac{1}{2}$

$\displaystyle sin(135)=sin(90+45)=sin(90).cos(45)+cos(90).sin(45 )$

$\displaystyle tan(-180)=tan(180)=tan(0)=0$

$\displaystyle cos(-270)=cos(360+(-270))=cos(90)=0$

Hope this helps