Question

If secA = 5/4 prove that cos²A = 1- sin²A

Answer 1

if secA=5/4

then,

cosA=4/5 and sinA=3/5

(4/5) ^2=1-(3/5)^2

16/25=1-9/25

16/25=16/25

( or)

according to trignometric identities

sin^2A+cos^2A=1

then,

cos^2A=1-sin^2A

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