Advertisements
Advertisements
प्रश्न
If A = B = 60°, verify that: cos(A - B) = cosA cosB + sinA sinB
Advertisements
उत्तर
cos(A - B) = cosA cosB + sinA sinB
L.H.S. :
cos(60° - 60°) = cos0° = 1
R.H.S. :
cosA cosB + sinA sinB
= cos60° cos60° + sin60° sin60°
= `(1)/(2) xx (1)/(2) + sqrt(3)/(2) xx sqrt(3)/(2)`
= `(1)/(4) + (3)/(4)`
= `(4)/(4)`
= 1
L.H.S. = R.H.S.
Therefore,
cos(A - B) = cosA cosB + sinA sinB.
APPEARS IN
संबंधित प्रश्न
If 4 sin2 θ – 1 = 0 and angle θ is less than 90°, find the value of θ and hence the value of cos2 θ + tan2 θ.
Find the value of 'A', if 2cos 3A = 1
If θ < 90°, find the value of: sin2θ + cos2θ
In the given figure, PQ = 6 cm, RQ = x cm and RP = 10 cm, find
a. cosθ
b. sin2θ- cos2θ
c. Use tanθ to find the value of RQ
Find the value of 'x' in each of the following:
Find the value 'x', if:
Find the value 'x', if:
Find the value 'x', if:
In the given figure; ∠B = 90°, ∠ADB = 30°, ∠ACB = 45° and AB = 24 m. Find the length of CD.
If cos3θ = sin(θ - 34°), find the value of θ if 3θ is an acute angle.
