Using trigonometric tables, find the value of (sin64∘42′ + cos42∘20′)
1.6433
We have
sin64∘42′ = 0.9041
42∘20′ = 42∘18′ + 2′
Now, cos42∘18′ = 0.7396
Mean difference for 2’ = 0.0004 [To be subtracted]
So, cos42∘20′ = 0.7392
Hence, sin64∘42′ + cos42∘20′ = 0.9041 + 0.7392 = 1.6433