Question

1, When a chord of a circle subtended an angle at point on the circle is 50°, if the radius is 3.5cm find the length of chord?

2, Length of a chord of a circle is 10.5cm and radius of the circle is 6.5cm. When the chord is subtend an angle at a point on the circle, what is the measure of the maximum angle?

Please answers me the correct answer. Then I will be mark you as a brainlist. Those who gave me correct answers only..​

Answer 1

Step-by-step explanation:

we have to find the value of cos20° cos100° + cos100° cos140° - cos140° cos200°

solution : cos20° cos100° + cos100° cos140° - cos140° cos200°

= cos100° [ cos20° + cos140° ] - cos140° cos200°

using formula, cosC + cosD = 2cos(C + D)/2 cos(C - D)/2

= cos100° [2cos80° cos60°] - cos140° cos200°

= cos100° [ 2 cos80° × 1/2 ] - cos140° cos200°

= cos100° cos80° - cos140° cos200°

= 1/2 [ 2cos100° cos80° - 2cos140° cos200°]

using formula,

2cosA cosB = cos(A + B) + cos(A - B)

= 1/2 [ cos180° + cos20° - (cos340° + cos60°)]

= 1/2 [ -1 + cos20° - cos340° - 1/2 ]

= 1/2 [ -3/2 + cos20° - cos(360° - 20°)]

= 1/2 [ -3/2 + cos20° - cos20°]

= 1/2 × (-3/2)

= -3/4

Therefore the value of cos20° cos100° + cos100° cos140° - cos140° cos200° = -3/4