Page 45 - DMTH201_Basic Mathematics-1
P. 45
Basic Mathematics – I
Notes
and cosec =
cos x =
–1
=
=
=
Property 8
–1
–1
(i) sin x + sin y =
–1
–1
(ii) cos x + cos y =
–1
–1
(iii) sin x – sin y =
–1
(iv) cos x – cos y =
–1
Proof
(i) Let x = sin , y = sin , then
L.H.S. = q + f
R.H.S. =sin (sin cos + cos sin )
–1
=
L.H.S. = R.H.S
(ii) Let x = cos and y = cos
L.H.S. = +
–1
R.H.S. = cos (cos cos – sin sin )
=
L.H.S. = R.H.S
(iii) Let x = sin , y = sin
L.H.S. = –
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