Question

Use 15◦= 45◦− 30◦to find the exact value of sin15 , cos15 , tan15

Answer 1

sin(x-y)=sinxcosy-sinycosx cos(x-y)=cosxcosy+sinxsiny.......tan(x-y)=sin(x-y)/cos(x-y)....try it !!!!! :D

Answer 2

others are similar
damn i made a mistake hold on

Answer 3

\[\sin(15)=\sin(45-30)=\sin(45)\cos(30)-\sin(30)\sin(45)\]
\[=\frac{\sqrt{2}}{2}\times \frac{\sqrt{3}}{2}-\frac{\sqrt{2}}{2}\times \frac{1}{2}\]
\[\frac{\sqrt{6}}{4}-\frac{\sqrt{2}}{4}=\frac{\sqrt{6}-\sqrt{2}}{4}\]
that's better

Answer 4

what formula do i use for cos though ?

Answer 5

you have a formula above...just plug in 45 for x and 15 for y....try to learn!!!! :D