NCERT Exemplar Solutions
Class 10 - Mathematics - CHAPTER 8: Introduction to Trignometry and Its Applications - Exercise 8.2
Question 2

Question. 2

The value of the expression \(\cos^2 23^\circ-\sin^2 67^\circ\) is positive.

Answer:

False.

Detailed Answer with Explanation:

Step 1: Recall the trigonometric identity: \(\sin(90^\circ - \theta) = \cos \theta\).

Step 2: Here, we have \(\sin 67^\circ\). Notice that \(67^\circ = 90^\circ - 23^\circ\).

Step 3: So, \(\sin 67^\circ = \sin(90^\circ - 23^\circ) = \cos 23^\circ\).

Step 4: Substitute this value into the expression: \(\cos^2 23^\circ - \sin^2 67^\circ = \cos^2 23^\circ - (\cos 23^\circ)^2\).

Step 5: Simplify: \(\cos^2 23^\circ - \cos^2 23^\circ = 0\).

Step 6: The result is \(0\). Since 0 is neither positive nor negative, the statement “the value is positive” is False.

NCERT Exemplar Solutions Class 10 – Mathematics – CHAPTER 8: Introduction to Trignometry and Its Applications – Exercise 8.2 | Detailed Answers