Advertisements
Advertisements
प्रश्न
If 4 cos2 A – 3 = 0 and 0° ≤ A ≤ 90°, then prove that cos 3 A = 4 cos3 A – 3 cos A
उत्तर
L.H.S. = cos 3A = cos 90° = 0
R.H.S. = 4 cos3 A – 3 cos A
= 4 cos3 30° – 3 cos 30°
= `4 (sqrt3/2)^3 - 3(sqrt3/2)`
= `(4 xx 3sqrt(3))/8 - (3sqrt(3))/2`
= `(3sqrt(3))/2 - (3sqrt(3))/2 = 0`
L.H.S. = R.H.S.
APPEARS IN
संबंधित प्रश्न
Prove the following trigonometric identities.
(cosecA − sinA) (secA − cosA) (tanA + cotA) = 1
Evaluate:
14 sin 30° + 6 cos 60° – 5 tan 45°
If the angle θ = –45° , find the value of tan θ.
If 3 cot θ = 4, find the value of \[\frac{4 \cos \theta - \sin \theta}{2 \cos \theta + \sin \theta}\]
If A + B = 90° and \[\cos B = \frac{3}{5}\] what is the value of sin A?
Write the value of tan 10° tan 15° tan 75° tan 80°?
If A and B are complementary angles, then
The value of cos 1° cos 2° cos 3° ..... cos 180° is
Express the following in term of angles between 0° and 45° :
cos 74° + sec 67°
If tan θ = cot 37°, then the value of θ is
