Final answer:
To simplify a trigonometric expression in terms of cosx, we can apply trigonometric identities to eliminate the sine terms and express the entire expression using only cosine terms.
Step-by-step explanation:
The student's question relates to the simplification of a trigonometric expression and expressing it in terms of cosx. Given the various trigonometric identities such as sin 2θ = 2sin θcos θ, cos 2θ = cos² θ - sin² θ = 2 cos² θ - 1 = 1 - 2 sin² θ, and relationships in a right triangle, we can rewrite expressions that involve sine in terms of cosine. For example, using the identity sin² θ = 1 - cos² θ, we can substitute sin² θ in an expression with cos² θ to simplify it.
To answer the student's question, we would apply these identities and algebraically manipulate the given trigonometric expression to cancel out any terms involving sine and leave only terms involving cosine. If the student provided a specific expression, we would show step-by-step how to apply the relevant identities and algebra to reach the simplified form in terms of cosx.