The proof of the identity that justifies that ( 1 - cos²x ) secx equals sinx(tanx) has been described below with statements and rules.
Statement 1; ( 1 - cos²x ) secx
This is given
Statement 2; sin²x · secx
Rule 1; From trigonometric identities, we know that;
sin²x + cos²x = 1,
Thus; cos²x = 1 - sin²x
Thus; ( 1 - cos²x ) secx = sin²x · secx
Statement 3; sin²x (1/cosx)
Rule 2; The rule here according to trigionometric identities is that; secx = 1/cosx. Thus; secx = 1/cosx .
Statement 4; sinx (sinx/cosx )
Rule 3; The rule here is that sin²x can be expressed as (sinx * sinx)
Thus, we have; sinx . sinx (1/cosx) = sinx (sinx/cosx ).
Statement 5; sinx(tanx)
Rule 4; The rule here is that; sinx/cosx = tanx.
Thus; sinx (sinx/cosx ) gives us sinx(tanx)
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