using the cosine Difference Formula. 1. Find an equivalent form of cos(π 2 − θ) using the cosine difference formula. cos(π 2 − θ) = cosπ 2cosθ + sinπ 2sinθ cos(π 2 − θ) = 0 × cosθ + 1 × sinθ, substitute cosπ 2 = 0 and sinπ 2 = 1 cos(π 2 − θ) = sinθ. We know that is a true identity because of our understanding of the simplify\:\frac{\sin^4(x)-\cos^4(x)}{\sin^2(x)-\cos^2(x)} simplify\:\frac{\sec(x)\sin^2(x)}{1+\sec(x)} \sin (x)+\sin (\frac{x}{2})=0,\:0\le \:x\le \:2\pi The cosine and sine functions, cos (x) and sin (x), are defined with a unit circle. cos (x) and sin (x) are, respectively, the horizontal and vertical coordinates of a point moving along the circumference of the circle. We learn how to use the unit circle and define both the cosine and sine functions. As required. Hopefully this helps! Answer link. Use the sum in cosine identity, cos (A+ B) = cosAcosB - sinAsinB. Thus we have: cos (180˚)cos (x) - sin (180˚)sinx = -cosx -1 (cosx) - 0 (sinx)= -cosx -cosx= -cosx LHS = RHS As required. Hopefully this helps! Vay Tiền Nhanh Chỉ Cần Cmnd.

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