- Home
- Standard 10
- Mathematics
8. Introduction to Trigonometry
easy
If $\sec 4 A =\operatorname{cosec}\left( A -20^{\circ}\right),$ where $4 A$ is an acute angle, find the value of $A$. (in $^{\circ}$)
A
$110$
B
$22$
C
$50$
D
$90$
Solution
Given that,
$\sec 4 A =\operatorname{cosec}\left( A -20^{\circ}\right)$
$\operatorname{cosec}\left(90^{\circ}-4 A \right)=\operatorname{cosec}\left( A -20^{\circ}\right)$
$90^{\circ}-4 A = A -20^{\circ}$
$110^{\circ}=5 A$
$A=22^{\circ}$
Standard 10
Mathematics