Question

Value cos square 15 - sin square 15

Answer 1

$Value \: of \: cos^{2} 15 \degree - sin^{2} 15 \degree \\= cos \: (2 \times 15 )$

$\boxed {\pink { Since, \:cos^{2} A - sin^{2} A = cos 2A }}$

$= cos 30\degree \\= \Big( \frac{\sqrt{3}}{2}\Big)^{2} \\= \frac{\sqrt{3}^{2}}{4} \\= \frac{3}{4}$

Therefore.,

$\red {Value \: of \: cos^{2} 15 \degree - sin^{2} 15 \degree }\green {= \frac{3}{4} }$

•••♪

Answer 2

Step-by-step explanation:

formula,

cos²A - sin ²B= cos (A+B) cos (A-B)

COS²15°-SIN²15°=COS (15+15) COS(15-15)

COS² 30°.COS² 0°

√3/2.1

√3/2

NOW SQUARE,DUE TO QUESTION IS IN THE SQUARE FORM

SO, (√3/2)²

3/4