Question

if cos a+ sec a =2 show that cos 8 a + sec 8a = 2
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Answer 1

Step-by-step explanation:

cos a+sec a=2

cos a+(1/ cos a) =2

(cos²a+1)/cos a=2

cos²a+1=2cos a

cos²a-2cos a+1=0

(cos a-1) ²=0

cos a=1

cos2a=2cos²a-1

=2(1)-1

=1

Similarly cosNa=1

where N is an integer

Hence

cos8a=1

sec8a=(1/cos8a) =1/1=1

cos 8a+sec 8a=1+1=2