Question

13. Find the value of
sin?A + cos2A
sec2A - tan²A
?​

Answer 1

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Given

sin?A + cos2A

sec2A - tan²A

?​

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$tan^4a+tan^2a=1$

$=>(tan^2a+1)tan^2a=1$

$=>sec^2atan^2a=1$

$=>(1/cos^2a)tan^2a=1$

$=>tan^2a=cos^2a$

$=>sin^2a/cos^2a=cos^2a$

$=>sin^2a=cos^4a$

$=>1-cos^2a=cos^4a$

$=>cos^4a+cos^2a=1$