Question 92

If $$2cos^2A - 1 = x$$, then the value of x is

Solution

Expression : $$2cos^2A - 1 = x$$

$$\because$$ $$(sin^2A+cos^2A=1)$$

= $$2cos^2A-(sin^2A+cos^2A)$$

= $$2cos^2A-cos^2A-sin^2A$$

= $$cos^2A-sin^2A = (cos^2A-sin^2A) \times (1)$$

= $$(cos^2A-sin^2A) \times (cos^2A+sin^2A)$$

= $$cos^4A-sin^4A$$

=> Ans - (B)

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