The expression cos (pi/2 − theta) captures a fundamental relationship between cosine and sine. Geometrically, this comes from looking at a right triangle. If theta is one acute angle, then pi/2 − theta is the other acute angle, since the two must add up to a right angle. The cosine of an angle is defined as the ratio of the adjacent side to the hypotenuse, while the sine of the complementary angle uses the opposite side over the same hypotenuse. Because the side opposite one angle is the adjacen

TRIGONOMETRY IDENTITIES: Trigonometric identities are mathematical equations that are true for all values of the variables involved, where both sides of the equation are defined. They are essential tools for simplifying trigonometric expressions and solving equations. These identities are derived from the definitions of trigonometric functions and the Pythagorean theorem. MAJOR TRIGONOMETRY IDENTITIES Reciprocal Identities: These relate each trigonometric function to its reciprocal: csc θ = 1/si