Question

General Identities
(in Trigonometry)
ADDITION AND SUBTRACTION IDENTITIES

FIND THE VALUE OF:
sin 15 degrees

Answer 1

@chmvijay

Answer 2

\[\sin 15=\sin \left( 45-30 \right)=\sin 45\cos 30-\cos 45\sin 30\]
\[\sin 45=\frac{ 1 }{ \sqrt{2} },\cos 45=\frac{ 1 }{ \sqrt{2}},\sin 30=\frac{ 1 }{ 2 },\cos 30=\frac{ \sqrt{3} }{ 2 }\]
solve.

Answer 3

where and how did you get sin (45-30) ????
@surjithayer

Answer 4

simple math 45-30=15
you can also take 60-45=15

Answer 5

oh does it give the same answer?

Answer 6

if i use either?
@surjithayer

Answer 7

yes
remember
\[\sin 60=\frac{ \sqrt{3} }{ 2 },\cos 60=\frac{ 1 }{ 2 },\]

Answer 8

how do you know if the ooperation is + or -
@surjithayer

Answer 9

how do you know if the ooperation is + or -
at sin (45-30)
???
@surjithayer

Answer 10

@Preetha @thomaster @ParthKohli

Answer 11

Hmm! Are you aware that 15 = 45 - 30?

Answer 12

we know t-ratios of 0,30,45,60,90

Answer 13

divide each by 4 and take the square root.

Answer 14

@ParthKohli yes i am

Answer 15

so sin30 becomes\[\frac{ \sqrt{4} }{ 4 }\]
?
is it like that?
then wht's the point?
please help me.
i really bad at this and anything related to numbers

@surjithayer

Answer 16

\[\sqrt{\frac{ 4 }{4 }}=\sqrt{1}=1\]

Answer 17

\[\sqrt{\frac{ 3 }{ 4 }}=\frac{ \sqrt{3} }{ 2 }\]

Answer 18

\[\sin 30=\sqrt{\frac{ 1 }{4 }}=\frac{ 1 }{2 }\]

Answer 19

i see

what about tan?

Answer 20

\[\sin 90=\sqrt{\frac{ 4 }{4 }}=\sqrt{1}=1\]

Answer 21

\[\tan 0=\frac{ \sin 0 }{ \cos 0 }=\frac{ 0 }{ 1 }=0\]

Answer 22

\[\tan \theta =\frac{ \sin \theta }{ \cos \theta } \]

Answer 23

okay thanks
i'll try and figure this out..