10th Class Mathematics Introduction to Trigonometry Question Bank Case Based MCQs - Introduction to Trigonometry

The value of \[{{\sin }^{2}}\theta +{{\cos }^{2}}\theta \] is

A) 0

B) 1

C) -1

D) 2

Correct Answer: B

Solution :

\[{{\sin }^{2}}\theta +{{\cos }^{2}}\theta ={{\left( \frac{PR}{PQ} \right)}^{2}}+{{\left( \frac{QR}{PQ} \right)}^{2}}\]

\[={{\left( \frac{9}{15} \right)}^{2}}+{{\left( \frac{18}{15} \right)}^{2}}=\frac{81+144}{225}=\frac{225}{225}=1\]