1.

\operatorname { sec } ( \frac { \pi } { 4 } + x ) \operatorname { sec } ( \frac { \pi } { 4 } - x ) = 2 \operatorname { sec } 2 x

Answer»

Sec(45+a)sec(45-a)

=> 1/cos(45 + a)*cos(45 -a)

=> 1/(cos45cosa – sin45sina) (cos45cosa+sin45sina)

=> 2/(cosa -sina) (cosa + sina)

=> 2/(cos^2a -sin^2a)

=> 2/cos2a

=> 2sec2a



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