Question

tan48 tan23 tan 42 tan 67= 1

Answer 1

tan48 tan23 tan 42 tan 67
=tan (90° − 42°) tan (90° − 67°) tan 42° tan 67°
=cot 42° cot 67° tan 42° tan 67
= (cot 42° tan 42°) (cot 67° tan 67°)
=(1)(1)
=1

Answer 2

LHS


Tan48 tan42 tan23 tan 67

Tan48*tan(90-48)*tan23*tan(90-23)

Tan48*cot48*tan23*cot23

As cot =1/tan


Then

{(Tan48*1)/tan48} *{(tan23*1)/tan23}


1*1

=1

LHS =1

RHS =1

LHS=RHS


I hope this much will help