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education/math/MATH1060 (trig)/Identities.md

@@ -42,7 +42,7 @@ $$ sin^2\theta $$
 ### Finding all values using identities
 If $sec\theta = -\frac{25}{7}$ and $0 < \theta < \pi$, find the values of the other 5 trig functions:
 
-Using the trig identity $1 + tan^2\theta = cot^2\theta$, we can do this:
+1. To find $tan\theta$, we can use the trig identity  $1 + tan^2\theta = sec^2\theta$:
 $$ 1 + tan^2\theta = (-\frac{25}{7})^2 $$
 Shuffling things around, we get this:
 $$ tan^2\theta = \frac{625}{49} - 1 $$
@@ -54,3 +54,5 @@ You can get rid of the exponent:
 $$ \sqrt{\frac{576}{49}} = tan\theta $$
 $\sqrt{576} = 24$ and $\sqrt{49} = 7$, so:
 $$ tan\theta = \frac{24}{7} $$
+2. To find $cos\theta$, because $sec$ is the inverse of $cos$, we can use the identity $sec\theta = \frac{1}{cos\theta}$:
+So $cos\theta = -\frac{7}{25}$.