Answer? .,

Step-by-step explanation:

what is the formula for the whole surface area of a sphere ?

that would give us the whole surface area all 360 degrees or 2×pi arc length all around the sphere.

but we don't need all 360 degrees. we only need the Theta'th (that is the specified angle) part.

in radians the arc length of that angle segment on the "equator" of the sphere

s = r×Theta

and the whole equator circumference is

c = 2×pi×r

so, the Theta'th part is then

r×Theta / 2×pi×r = Theta / 2×pi

we only need that part of the whole sphere surface area, so the formula would look like

=>

b. an equilateral triangle inscribed in a circle

step-by-step explanation:

we are given the figure of two circles having a triangle inside.

now, we know that,

"when a figure is lying inside an another figure, then the outside figure is known as circumscribed figure and the figure lying inside is referred to as the inscribed figure".

as we see that, the circles are containing the triangle completely.

thus, the circles are the circumscribed figures and the triangle is the inscribed figure.

hence, we get, 'an equilateral triangle is inscribed in a circle'.

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step-by-step explanation: