If \(\sin x-\cos x=\frac{1}{2}\), what is the value of \(\sin x\cos x\)?
Answer and explanation
Correct answer: \(\frac{3}{8}\)
Use \((\sin x-\cos x)^2=\sin^2x+\cos^2x-2\sin x\cos x=1-2\sin x\cos x\). Since \(\sin x-\cos x=\frac{1}{2}\), we get \(\frac{1}{4}=1-2\sin x\cos x\). Hence \(2\sin x\cos x=\frac{3}{4}\), so \(\sin x\cos x=\frac{3}{8}\). The value \(\frac{1}{4}\) is the square of the given difference, not the product. Exam tip: square the given expression first and then use \(\sin^2x+\cos^2x=1\).
Frequently asked questions
What is the correct answer to this question?
\(\frac{3}{8}\)
Why is this the correct answer?
Use \((\sin x-\cos x)^2=\sin^2x+\cos^2x-2\sin x\cos x=1-2\sin x\cos x\). Since \(\sin x-\cos x=\frac{1}{2}\), we get \(\frac{1}{4}=1-2\sin x\cos x\). Hence \(2\sin x\cos x=\frac{3}{4}\), so \(\sin x\cos x=\frac{3}{8}\). The value \(\frac{1}{4}\) is the square of the given difference, not the product. Exam tip: square the given expression first and then use \(\sin^2x+\cos^2x=1\).
Which subject and chapter does this question cover?
This is a Class 12 Mathematics question. Chapter: Trigonometric Functions. Topic: Trigonometric functions and their properties.
