Question

The value of sin69°45' - sin15°40' is .

• A. 0.8311
• B. 0.2223
• C. 0.6683

Answer 1

The correct option is C 0.6683

We can write,
69°45' = 69°42' + 3'
From the table we have, sin69°42' = 0.9379
Mean difference for 3′ = 3 (Mean difference to be added for sine)
sin69°42' = 0.9379
3′ = + 3
____________________
sin69°45' = 0.9383 ... (i)


We can write,
15°40' = 15°36' + 4'
From the table we have, sin15°36' = 0.2689
Mean difference for 4′ = 11 (Mean difference to be added for sine)
sin15°36' = 0.2689
4′ = + 11
____________________
sin15°40' = 0.2700 ... (ii)

From equations (i) and (ii), we get
sin69°45' - sin15°40' = 0.9383 - 0.2700 = 0.6683