Mathematics
Use tables to find cosine of :
(i) 2° 4'
(ii) 8° 12'
(iii) 26° 32'
(iv) 65° 41'
(v) 9° 23' + 15° 54'
Trigonometric Identities
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Answer
(i) From table,
cos 2° 6' = 0.9993
Difference of 2' = 0 [To add]
∴ cos 2° 4' = 0.9993 + 0 = 0.9993
Hence, 2° 4' = 0.9993
(ii) From table,
cos 8° 12' = 0.9898
Hence, 8° 12' = 0.9898
(iii) From table,
cos 26° 30' = 0.8949
Difference of 2' = 0.0003 [To subtract]
∴ cos 26° 32' = 0.8949 - 0.0003 = 0.8946
Hence, 26° 32' = 0.8946
(iv) From table,
cos 65° 42' = 0.4115
Difference of 1' = 0.0003 [To add]
∴ cos 65° 41' = 0.4115 + 0.0003 = 0.4118
Hence, 65° 41' = 0.4118
(v) Adding,
9° 23' + 15° 54' = 24° 77' = 25° 17'
(As, 60' = 1°)
From table,
cos 25° 18' = 0.9041
Difference of 1' = 0.0001 [To add]
∴ cos 25° 18' = 0.9041 + 0.0001 = 0.9042
Hence, 25° 18' = 0.9042
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