258
a)
[tex]sin(x+60)=sin(x)cos(60)+cos(x)sin(60) \\ cos(60)=\frac12 \\ sin(60)=\frac{\sqrt{3}}{2} \\ sin(x+60)=\frac12sin(x)+\frac{\sqrt{3}}{2}cos(x)[/tex]
b)
[tex]\frac12sin(x)+\frac{\sqrt{3}}{2}cos(x)=\frac12 \, , \, x\in[0,360> \\ sin(x+60)=\frac12 \\ sin(30)=\frac12 \, \wedge \, sin(150)=\frac12 \\ x=-30\, \vee \, x=90[/tex]
259
a)
[tex]sin \, 2v\, =sin\,v+2\,=sin\,v \,cos \,v \,+cos\,v\,sin\,v\,=sin\,v\,cos\,v\,+sin\,v\,cos\,v\,=2sin\,v\,cos\,v\,[/tex]
b)
[tex]cos\,2v\,=cos\,v\,cos\,v\,-sin\,v\,sin\,v\,=cos^2v-sin^2v[/tex]
c)
[tex]tan\,2v\,=\frac{sin\,2v}{cos\,2v}=\frac{2sin\,v\,cos\,v\,}{cos^2v-sin^2v} \\ cos^2v-sin^2v=(cos\,v\,+sin\,v)(cos\,v\,-sin\,v)[/tex]
Kan jeg få et hint om hva jeg bør gjøre her?
260
[tex]sin(u+v)=sin\,u\,cos\,v\,+sin\,v\,cos\,u\,=\frac14cos\,v\,+\frac13cos\,u \\ cos(v)=\frac{2\sqrt{2}}{3} \\ cos(u)=\frac{\sqrt{15}}{4} \\ \frac14\cdot\frac{2\sqrt{2}}{3}+\frac13\cdot\frac{\sqrt{15}}{4}=\frac{2\sqrt{2}+\sqrt{15}}{12}=\frac{\sqrt{2}+\sqrt{15}}{6}[/tex]
[tex]sin(u-v)=\frac{\sqrt{2}-\sqrt{15}}{6}[/tex]
[tex]sin(v-u)=\frac{\sqrt{15}-\sqrt{2}}{6}[/tex]
261
a)
[tex]sin \, 3v\,=sin\,2v\,cos\,v\,+sin\,v\,cos\,2v=2sin\,v\,cos^2v\,+sin\,v\,(cos^2v-sin^2v) \\ 2sin\,v\,cos^2v+sin\,v\,cos^2v-sin^3v=3sin\,v\,cos^2v-sin^3v[/tex]
Kan noen gi meg et hint om hva jeg må gjøre nå?
b)
[tex]cos\,3v=cos\,v\,cos\,2v\,-sin\,v\,sin\,2v=cos\,v\,(cos^2v-sin^2v)-sin\,v\,(2sin\,v\,cos\,v) \\ cos^3v-sin^2v\,cos\,v-2sin^2v\,cos\,v=cos^3v-3sin^2v\,cos\,v[/tex]
Kan noen gi meg et hint om hva jeg må gjøre nå?