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(i) tan 48° tan 23° tan 42° tan 67° = 1 

(ii) cos 38° cos 52° – sin 38° sin 52° = 0.

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(i) tan 48° tan 23° tan 42° tan 67° = 1 

LHS = tan 48° tan 23° tan 42° tan 67° 

= tan 48° × tan 23° × tan (90 – 48).tan (90 – 23) 

= tan 48° × tan 23° × cot 48° × cot 23°

= 1 

∴ LHS = RHS 

(ii) cos 38° cos 52° – sin 38° sin 52° = 0 

LHS = cos38° cos 52° – sin 38° sin 52° 

= cos 38° × cos (90 – 38) – sin 38° × sin (90 – 38) 

= cos 38° × sin 38° – sin 38° × cos 38° 

= 0

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