Without using tables, calculate the value of 1 + sec²30
A. 2 1/3
B. 2
C. 1 1/3
D. 3/2
Correct Answer: A
Explanation
To find the value of \(1 + \sec^2 30^\circ\) without using tables, follow these steps:
1. Recall the trigonometric identity:
\[
\sec^2 \theta = 1 + \tan^2 \theta
\]
2. Use this identity for \(\theta = 30^\circ\):
\[
\sec^2 30^\circ = 1 + \tan^2 30^\circ
\]
3. Find \(\tan 30^\circ\):
\[
\tan 30^\circ = \frac{1}{\sqrt{3}}
\]
4. Square \(\tan 30^\circ\):
\[
\tan^2 30^\circ = \left(\frac{1}{\sqrt{3}}\right)^2 = \frac{1}{3}
\]
5. Substitute into the identity:
\[
\sec^2 30^\circ = 1 + \frac{1}{3} = \frac{4}{3}
\]
6. Calculate \(1 + \sec^2 30^\circ\):
\[
1 + \sec^2 30^\circ = 1 + \frac{4}{3} = \frac{3}{3} + \frac{4}{3} = \frac{7}{3}
\]
7. Convert to mixed fraction (if needed):
\[
\frac{7}{3} = 2 \frac{1}{3}
\]
Therefore, the correct answer is:
A. \(2 \frac{1}{3}\)