Question

In A ABC, if a=10 and R=5 then find angle A.​

Answer 1

Answer:

90 degree

Step-by-step explanation:

SinA/a =1/2R

SinA = a/2R

= 10/2(5)

= 1

SinA=1

Angle A =90degree

Answer 2

Answer:

Angle A=90 degrees

Step-by-step explanation:

Given that in triangle ABC,  

a=10

a is the length of  the side opposite to angle A

R=5

R is the radius

formula we use 2R=a/sinA

2R= a/sinA

2*5=10/sinA

10 =10/sinA

∴sinA=1

we know that sin90=1

⇒   angle A=90 degrees

    angle A= π/2 radians

then the angle A=90 degrees

therefore in a triangle ABC , the angle A=90 degrees