METHOD OF USING TRIGONOMETRIC TABLE

Example 1 :

Find the value of the following:

(i)  sin 49°

Solution :

sin 49°  =  0.7547

(ii) cos 74° 39'

Solution :

cos 74° 39' 

=  cos 74° 36' + 3'

=  0.2656 - 0.008

=  0.2648

(iii) tan 54° 26'

Solution :

tan 54° 26'  =  tan 54° 24' + 2''

  =  1.3968 + 0.0017

  =  1.3985

(iv) sin 21° 21'

Solution :

sin 21° 21'  =  sin 21° 18' + 3''

  =  0.3633 + 0.0008

  =  0.3641

(v) cos 33° 53'

Solution :

cos 33° 53'  =  cos 33° 48' - 5''

  =  0.8310 - 0.0008

  =  0.8302

(vi) tan 70° 17'

Solution :

tan 70° 17'  =  tan 70° 12' + 5''

  =  2.2776 + 0.0131

=  2.2907

Example 2 :

Find the value of θ if

(i) sin θ = 0.9975 (ii) cos θ = 0.6763 (iii) tan θ = 0.0720

Solution :

(i)  sin θ = 0.9975 

  =  sin 85° 57'

(ii) cos θ = 0.6763

  =  sin 47° 27'

(iii) cos θ = 0.6763

  =  sin 4° 7'

(iv) cos θ = 0.0410

  =  sin 87° 39'

(v) cos θ = 7.5958

  =  cos 82° 30'

Find the value of the following:

(i) sin 65° 39' + cos 24° 57' + tan 10° 10'

Solution :

sin 65° 39'  =  sin 65° 36' + 3''

  =  0.9107 + 0.0004

  =  0.9111

cos 24° 57'  =  0.9070 - 0.0004

=  0.9066

 tan 10° 10'  =  0.1781 + 0.0012

=  0.1793

sin 65°39'+cos 24°57'+tan 10°10'

  = 0.9111 + 0.9066 + 0.1793

=  1.997

(ii) tan 70° 58' + cos 15° 26' - sin 84° 59'

Solution :

tan 70° 58'  =  tan 70° 54' + 4''

  =  2.8878 + 0.0104

  =  2.8982

cos 15° 26'  =  cos 15° 24' - 2''

=  0.9641 - 0.0004

=  0.9637

sin 84° 59'  =  sin 84° 54' + 5''

=  0.9960 + 0.0002

=  0.9962

tan 70° 58' + cos 15° 26' - sin 84° 59' 

  =  2.8982 +  0.9637 - 0.9962 

  =  2.8657

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