נושא : שימוש בזהויות
sin ( 270 + α ) = − c o s α ? s i n α = s i n ( 180 − α ) s i n ( 180 − 270 − α ) = − c o s ( α ) s i n ( − 90 − α ) = − c o s ( α ) sin α = sin ( − α ) − s i n ( 90 + α ) = − c o s ( α ) s i n α = s i n ( 180 − α ) s i n ( 180 − 90 − α ) = c o s ( α ) s i n ( 90 − α ) = c o s ( α ) s i n ( 90 − α ) = c o s ( α ) {\displaystyle {\begin{aligned}&\sin(270+\alpha )=-cos\alpha ?\\&\color {blue}sin\alpha =sin(180-\alpha )\\&sin(180-270-\alpha )=-cos(\alpha )\\&sin(-90-\alpha )=-cos(\alpha )\\&\color {blue}\sin \alpha =\sin(-\alpha )\\&-sin(90+\alpha )=-cos(\alpha )\\&\color {blue}sin\alpha =sin(180-\alpha )\\&sin(180-90-\alpha )=cos(\alpha )\\&sin(90-\alpha )=cos(\alpha )\\&\color {blue}sin(90-\alpha )=cos(\alpha )\\\end{aligned}}}
sin ( 270 + α ) = − c o s α ? sin ( α ± β ) = sin α ∗ cos β ± cos α ∗ sin β s i n 270 ∗ c o s α + c o s 270 ∗ s i n α = − c o s α {\displaystyle {\begin{aligned}&\sin(270+\alpha )=-cos\alpha ?\\&\color {blue}\sin(\alpha \pm \beta )=\sin \alpha *\cos \beta \pm \cos \alpha *\sin \beta \\&sin270*cos\alpha +cos270*sin\alpha =-cos\alpha \\\end{aligned}}}
נחשב ערכים : sin ( 270 ) = − 1 cos ( 270 ) = 0 {\displaystyle {\begin{aligned}&\sin(270)=-1\\&\cos(270)=0\\\end{aligned}}}
s i n 270 ∗ c o s α + c o s 270 ∗ s i n α = − c o s α − 1 ∗ c o s α + 0 = − c o s α − c o s α = − c o s α {\displaystyle {\begin{aligned}&sin270*cos\alpha +cos270*sin\alpha =-cos\alpha \\&-1*cos\alpha +0=-cos\alpha \\&-cos\alpha =-cos\alpha \\\end{aligned}}}
