Question

1. Find the value of
(i) sin 210
(iii) tan 480°
(iv) sec 510
(ii) cos 315
Find the value of​

Answer 1

Answer:

Sin 210 = sin (270 - 60) = sin (3 x 90 - 60) = - cos 60 = - 1/2 <=ANS

Another Method:

sin 210 = sin (360 - 150)= - sin 150 = - sin (180 - 30) = - sin (2 x 90 - 30)

= - sin 30 [Since, 150 lies in 2nd quadrant & sin is +ve]

= - 1/2

Step-by-step explanation:

Hope it was helpful

Please please mark as brainliest

And follow me please

Answer 2

Answer:

sin (315)0

sin (315)0 = sin (90 x 3 + 45)

Since 315 lies in the 4th quadrant and in this quadrant sine function is negative , also 3 is an odd integer.

∴ sin (315)0 = sin (90 x 3 + 45) = - cos 45 = −12√

cos (210)0

cos (210)0 = cos(90 x 2 + 30)

Since 210 lies in the 3rd quadrant and in this quadrant cosine function is negative.Also the multiple of 90 is even.

∴ cos (210)0 = cos (90 x 2 + 30) = - cos 30 = −3√2

cos (480)

Solution : cos (480)0

cos (480)0 = cos(90 x 5 + 30)

Since 480 lies in the 2nd quadrant and in this quadrant cosine function is negative.Also the multiple of 90 is odd.

∴ cos (480)0 = cos (90 x 5 + 30) = -sin 30 = −12

We have,

cos (510)0 cos (330)0 + sin (390)0 cos (120)0

= cos(90 x 5 + 60) cos(90 x 3 + 60) + sin(90 x 3 + 30) cos(90 x 1 + 30)

= (- sin 60) (sin 60) + (sin 30)(- sin 30)

= −3√2×3√2+12×−12

= −34−14

= -1

∴ cos (510)0 cos (330)0 + sin (390)0 cos (120)0 = -1